Code cleanup

I touched a lot of code.

Mostly I just ran a PEP8 linter and fixed the errors it found. I also switched the `ApiErrorException` in the areas module to a `TypeError` and `raised` the exceptions instead of `return`ing them.

Podio is an important part of my employer's infrastructure and our applications are primarily written in python. More pull requests will follow. I believe very much in open source software and if I'm going to have to fix things (which I am) I'd prefer others benefit from it.
We try to keep the documentation style consistent, so arguments and return values doc is styled always in the same way. I would ask you to revert this to:

Arguments:
            item_id: Item's id
        Returns:
            Dict with item info