Add theming support

[ggoodman]

Embedding this library in 0.1.x in a project with a modern build step was very easy and provided an opportunity to adjust and/or overwrite styles.

For example, I would like to use a different font-size and font-family. I don't think the library should be hard-coded with those sorts of decisions already made and set in stone.

For now I need to use !important rules but hope you consider an disableStyles or similar option and add relevant classNames back to nodes in the tree to facilitate 3rd party theming.

Cheers, great module!

[xyc]

@ggoodman Inline styles are discussed in #4

• disableInlineStyles could be an option
• or add theme props for customization

For now, you can fork the repo and change inline styles.

[mathew-kurian]

@ggoodman +1. Currently using 9e06fc1 (npm 1.6). Great work however!