Added Read the Docs support

[jordiferrero]

Hi all,

I have wanted to do this for very long... I have now added support for the read the docs. This means that we can have explanations on the functions we write/methodologies in a nice formatted way.

As far as I am aware, such guides can be added to user_guide/file.rst. Feel free to add content there. I have a list of pages I would like to add for the analysis of PL data (coming soon). @jlaehne Maybe you could take care on the Jacobian transform documentation if you feel like explaining in a bit more detail how LumiSpy does this transform. That'd be a great opportunity to test it out too.

I believe having this will help external users to get started, as a nicely explained guide (like the EDX analysis page in HyperSpy docs) can really become "the place to check" on how to do data analysis of a particular data signal. I think the demo notebooks are great, but they can also get a bit messy.

Happy to hear suggestions!

PS: The Read the docs should trigger a build every time there is a merge. It will loop though all the docstrings and update the docs automatically.