Adding Python3 grammar

[NoZip]

Adds Python3 as a separate grammar. This grammar scope is 'source.python.3' in order to be recognized by all other tools as a Python grammar.

This Grammar is based on Python 3.5.1

Features

• Support for all string prefixes: u or no prefix for unicode strings, r for raw unicode strings, b for bytes string, and rb or br for raw bytes strings.
• New async and await keywords. async is defined as a 'storage.modifier.coroutine'.
• Revamped builtin functions and exceptions.

Exemple:

PS: Sorry for the double pull, some lines on the specs verification script have to be changed

[incognick]

This would be nice to get merged. Atom is missing python 3 grammar.

[ghost]

Please merge, I still cant figure out how to get Atom to pick up Python 3 if Python 2 is the default in the system..

[Kriechi]

Python 3 support would be really nice to have!

[MickaelBergem]

This looks like an important but old PR, what is preventing it from being merged?

[ambv]

language-python is switching to TreeSitter. The old regex-based grammar is on live support and unlikely to receive large changes anymore.