use SSE to add/subtract histograms
Rewrite histogram operations to remove GPL license on Perreault's code
fix UTF-8
remove typedef, use numpy type in its place
add casts to suppress compiler warnings
move _histogram.h to _shared/vectorized_ops.h, and copyright info to CONTRIBUTORS.txt
pep8
remove _histogram.h from setup.py, it's been moved to _shared
Merge pull request #432 from thouis/sse_ctmf

Use SSE/MMX/Altivec for faster CTMF