Fix module initialization to support both Python 2 and Python 3.
Fix module initialization to support both Python 2 and Python 3.

Handling of global_state still needs to be improved.

robbmcleod/numexpr,robbmcleod/numexpr,pydata/numexpr,pombredanne/numexpr,andreabedini/numexpr,robbmcleod/numexpr,andreabedini/numexpr,pydata/numexpr,pombredanne/numexpr,andreabedini/numexpr,pydata/numexpr,pombredanne/numexpr