Allow get_unpatched to be called to get unpatched version of a class or function, further harmonizing the interfaces.

Consolidate function patching and resolution of unpatched function, aligning pattern with the patched classes.

Move msvc import to avoid a circular import

Use EXT_SUFFIX instead of SO for py_limited_api renaming

Use LegacyVersion instead of LooseVersion

- Also apply the patch for numpy 1.11.2 pre release

Use LooseVersion instread of StrictVersion

Remove private prefix from monkey as monkey module explicitly declares that all functions are private.

Use pytest>=3.0.2

The bug that lead to pin it (pytest-dev/pytest#1888) was fixed in 3.0.2

Install py.test>=2.8,<3