Update docstrings and put documentation on http://readthedocs.org

[mgeier]

We could probably write our docstrings in NumPy format:
https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt

Probably the numpydoc extension for Sphinx could be used:
https://github.com/numpy/numpydoc

[mgeier]

Actually, sphinxcontrib.napoleon is better than numpydoc.

I tried it on another project (http://schunk.rtfd.org/) and it worked much better than numpydoc. Also, it will be included into Sphinx with the next release.

[bastibe]

As far as I can see, both documentation styles are roughly compatible with Numpy docstrings. I like the Numpy formatting.

[mgeier]

The documentation style would be the same either way. The two extensions just produce somehow differently formatted output.

[bastibe]

Work on this has started in #74

[mgeier]

I'm closing this because it was done in #74.
The result can be seen there: http://pysoundfile.rtfd.org.