Alabaster: a Sphinx theme

This theme is a modified "Kr" Sphinx theme from @kennethreitz (especially as used in his Requests project), which was itself originally based on @mitsuhiko's theme used for Flask & related projects.

A live example of what this theme looks like can be seen on e.g. paramiko.org.

Features (compared to Kenneth's original theme):

Easy ability to install/use as a Python package (tip o' the hat to Dave & Eric's sphinx_rtd_theme for showing the way);
Style tweaks, such as better code-block alignment, Gittip and Github button placement, page source link moved to footer, etc;
Additional customization hooks, such as header/link/etc colors;
Improved documentation for all customizations (pre-existing & new).

To use:

pip install alabaster (or equivalent command)
Enable the 'alabaster' theme + mini-extension in your conf.py:
```
import alabaster

html_theme_path = [alabaster.get_path()]
extensions = ['alabaster']
html_theme = 'alabaster'
html_sidebars = {
    '**': [
        'about.html', 'navigation.html', 'searchbox.html', 'donate.html',
    ]
}
```
- Modify the call to abspath if your _themes folder doesn't live right next to your conf.py.
- Feel free to adjust html_sidebars as desired - the theme is designed assuming you'll have about.html activated, but otherwise it doesn't care much.
  - See the Sphinx docs for details on how this setting behaves.
  - Alabaster provides about.html (logo, github buttom + blurb), donate.html (Gittip blurb/button) and navigation.html (a more flexible version of the builtin localtoc/globaltoc templates); the others listed come from Sphinx itself.
If you're using either of the image-related options outlined below (logo or touch-icon), you'll also want to tell Sphinx where to get your images from. If so, add a line like this (changing the path if necessary; see the Sphinx docs):
```
html_static_path = ['_static']
```
Add one more section to conf.py setting one or more theme options, like in this example (note: snippet doesn't include all possible options, see following list!):
```
html_theme_options = {
    'logo': 'logo.png',
    'github_user': 'bitprophet',
    'github_repo': 'alabaster',
}
```
The available theme options (which are all optional) are as follows:

Variables and feature toggles
- logo: Relative path (from $PROJECT/_static/) to a logo image, which will appear in the upper left corner above the name of the project.
  - If logo is not set, your project name setting (from the top level Sphinx config) will be used in a text header instead. This preserves a link back to your homepage from inner doc pages.
- logo_name: Set to true to insert your site's project name under the logo image as text. Useful if your logo doesn't include the project name itself. Defaults to false.
- logo_text_align: Which CSS text-align value to use for logo text (if there is any.)
- description: Text blurb about your project, to appear under the logo.
- github_user, github_repo: Used by github_button and github_banner (see below); does nothing if both of those are set to false.
- github_button: true or false (default: true) - whether to link to your Github.
  - If true, requires that you set github_user and github_repo.
  - See also these other related options, which behave as described in Github Buttons' README:
    - github_button_type: Defaults to watch.
    - github_button_count: Defaults to true.
- github_banner: true or false (default: false) - whether to apply a 'Fork me on Github' banner in the top right corner of the page.
  - If true, requires that you set github_user and github_repo.
- travis_button: true, false or a Github-style "account/repo" string - used to display a Travis-CI build status button in the sidebar. If true, uses your github_(user|repo) settings; defaults to false.
- gittip_user: Set to your Gittip username if you want a Gittip 'Donate' section in your sidebar.
- analytics_id: Set to your Google Analytics ID (e.g. UA-#######-##) to enable tracking.
- touch_icon: Path to an image (as with logo, relative to $PROJECT/_static/) to be used for an iOS application icon, for when pages are saved to an iOS device's home screen via Safari.
- extra_nav_links: Dictionary mapping link names to link targets; these will be added in a UL below the main sidebar navigation (provided you've enabled navigation.html.) Useful for static links outside your Sphinx doctree.
- sidebar_includehidden: Boolean determining whether the TOC sidebar should include hidden Sphinx toctree elements. Defaults to true so you can use :hidden: in your index page's root toctree & avoid having 2x copies of your navigation on your landing page.
- show_powered_by: Boolean controlling display of the Powered by Sphinx N.N.N. & Alabaster M.M.M section of the footer. When True, is displayed next to the copyright information; when False, is hidden.
Style colors

These should be fully qualified CSS color specifiers such as #004B6B or #444. The first few items in the list are "global" colors used as defaults for many of the others; update these to make sweeping changes to the colorscheme. The more granular settings can be used to override as needed.
- gray_1: Dark gray.
- gray_2: Light gray.
- gray_3: Medium gray.
- body_text: Main content text.
- footer_text: Footer text (includes links.)
- link: Non-hovered body links.
- link_hover: Body links, hovered.
- sidebar_header: Sidebar headers. Defaults to gray_1.
- sidebar_text: Sidebar paragraph text.
- sidebar_link: Sidebar links (there is no hover variant.) Applies to both header & text links. Defaults to `gray_1.
- sidebar_link_underscore: Sidebar links' underline (technically a bottom-border.)
- sidebar_search_button: Background color of the search field's 'Go' button.
- sidebar_list: Foreground color of sidebar list bullets & unlinked text.
- sidebar_hr: Color of sidebar horizontal rule dividers. Defaults to gray_3.
- anchor: Foreground color of section anchor links (the 'paragraph' symbol that shows up when you mouseover page section headers.)
- anchor_hover_fg: Foreground color of section anchor links (as above) when moused over. Defaults to `gray_1.
- anchor_hover_bg: Background color of above.
- note_bg: Background of .. note:: blocks. Defaults to gray_2.
- note_border: Border of same.
- footnote_bg: Background of footnote blocks.
- footnote_border: Border of same. Defaults to gray_2.
- pre_bg: Background of preformatted text blocks (including code snippets.) Defaults to gray_2.
- narrow_sidebar_bg: Background of 'sidebar' when narrow window forces it to the bottom of the page.
- narrow_sidebar_fg: Text color of same.
- narrow_sidebar_link: Link color of same. Defaults to gray_3.

Additional info / background

Fabric #419 contains a lot of general exposition & thoughts as I developed Alabaster, specifically with a mind towards using it on two nearly identical 'sister' sites (single-version www 'info' site & versioned API docs site).
Alabaster includes/requires a tiny Sphinx extension on top of the theme itself; this is just so we can inject dynamic metadata (like Alabaster's own version number) into template contexts. It doesn't add any additional directives or the like, at least not yet.

svenkreiss/alabaster

Alabaster: a Sphinx theme

Additional info / background