Type Variable Names

[jparise]

PEP 8 suggest some naming rules for type variables:

Names of type variables introduced in PEP 484 should normally use CapWords preferring short names: T, AnyStr, Num. It is recommended to add suffixes _co or _contra to the variables used to declare covariant or contravariant behavior correspondingly.

These might be useful additional checks to add to pep8-naming.