Add new Python 3.5/3.6 Syntax

[garetht]

This pull request adds several (but not all) new syntax features in Python 3.5 and 3.6.

• PEP 492 - Coroutines with async and await syntax
• PEP 465 - A dedicated infix operator for matrix multiplication
• PEP 526: Syntax for variable annotations
• PEP 530: Asynchronous Comprehensions
• PEP 498: Formatted string literals
• Only the dictionary unpacking syntax of PEP 448 - Additional Unpacking Generalizations

Additional tests have been added in https://github.com/bjpop/language-python-test/pull/1

[andreabedini]

@bjpop can this be merged?

[andreabedini]

<3