PEP8, update numpy issue links
Use the documented struct.calcsize to determine machine word size for better pypy support.
Merge pull request #20 from yuyichao/master

Use the documented struct.calcsize to determine machine word size for better pypy support.
workaround for pypy dtype hash
as_strided is fixed in numpy
workaround for pypy NotImplementedError
export hashability of complex dtypes
export dtype to key function
Merge pull request #21 from yuyichao/master

workaround for pypy dtype hash
Test whether as_strided preserves structured dtypes before using it