Write the getting started with coala tutorial in a jupyter notebook.

Rewriting it in jupyter, will allow us to add comments and actually let the users execute the code locally. It would be a more interactive and immersive experience for user.

Maybe we can include it already with `coala` and invoke it with `coala tutorial` maybe.

Thoughts @Adrianzatreanu ?

Locate the current getting-started tutorial in the coala documentation and review how existing documentation is organized. Clarify whether the scope is only an executable Jupyter notebook or also a `coala tutorial` command; done means the tutorial is interactive, locally runnable, and integrated into the documentation.

Written by the indexing model from the issue text.