Sphinx documentation

[rai-pranav]

Added documentation to various functions, and added sphinx related files.

[rai-pranav]

Fixes #16

[oliche]

This looks all good.
A few small changes before to commit this:

• it seems we have changed the docstring format to Google. No problem but this should be mentionned in the README.md in the contribution section.
• this README.md should not contain any documentation, but link to the actual sphinx website instead
• in the docs folder, there should be a README.md file explaining how to build the documentation. An example can be found here: https://github.com/int-brain-lab/ibldevtools/tree/master/00_dev_site, this small readme explains a dev how to build the doc
  Thanks for working on the documentation !

[rai-pranav]

@oliche I have add the changes you have requested. I would need to understand from you , how to create the documentation website (for e.g. docs.internationalbrainlab.org/ibleatools) . And then I can add it on the README.md file. For now, I am just referencing a index.rst file from the documentation.