General documentation needed

[joheinze]

We need to check the inline documentation for consistency

We also need to write a proper documentation for PriNCe in ./docs

The documentation shall contain:

• a short overview of the matrix equtations that are solved (adapted from my Thesis, chapter 4)
• a short tutorial on using the code
• references to the models used in the code (cross sections, photon fields, etc ...)
• an overview of the class structure
• . . .

The current docs are only a template taken from the MCEq documentation

[afedynitch]

The setup.py and initial sphinx docs are set up and can build to HTML. Look at the pull request for more details.

[joheinze]

I merged the pull request #14 with the basic layout.

Compiling did work fine for me!

[afedynitch]

So for the docs, we need the tutorial to work. There is an example from MCEq, as far as I understand people were quite happy with it. Would be happy if you can help with that :)