ENH Do not include Python in extern "C"
ENH Do not include Python in extern "C"

In newer versions of Python (3.4+), there is a Python header which uses
C++ templates, leading to errors if extern "C" is used.

Python.h is documented as being includeable from C.

Fixes #17

luispedro/imread,qbbian/imread,luispedro/imread,qbbian/imread,luispedro/imread