Description

This PR adds the suggested changes from #257 using the latest tree-sitter-python and API.

We are using:
'binary_operator > "@"': 'keyword.operator'

To avoid highlighting the @ in decorated_definition > decorator > "@" as keyword.operator in f.ex.:

@classmethod
def foo(*, arg1,arg2):
    ...

Open questions

1. When raising exception using the raise Exception('a') syntax. The exception is scoped as a function call (entity.name.function). Should Exception be support.type.exception in this case as well?

        raise ValueError('A very specific bad thing happened.')

2. Compared to #257 we are missing two functions:
   __build_class__
BuiltinImporter

I used the list from https://docs.python.org/3/library/functions.html when adding the current functions. Are these two functions and should be added?

Issues

Supersedes and closes #257
Fixes #295

/cc @ambv @maxbrunsfeld