First release checklist

[PabloCorcho]

Here's a (non-exhaustive) list of pending items to have ready before the first release version:

• [x] Add documentation to all relevant classes/methods (PR #24).
• [x] Design the contents to be included on the online documentation (#29).
• [x] Include a default SSP model for tutorials/demos (WI, #22).
• [ ] Refactor the directory tests (by tutorials) and test all methods.
• [ ] Create a release branch that does not include fitting_module.
• [ ] Release on pypi

[PabloCorcho]

@paranoya check tutorials

[PabloCorcho]

@Danieljl96 let us know if fitting module is ready for release

[paranoya]

Shall we mark "Refactor the directory tests (by tutorials) and test all methods"? I mean, "all"?