ENH: Add SimpleITK IO plugin.

IO plugin for SimpleITK, http://simpleitk.org/

imread and imsave implemented. Tests based off the PIL tests.
use SSE to add/subtract histograms
Rewrite histogram operations to remove GPL license on Perreault's code
fix: Otsu(8bit) and bilateral functions docstrings
Merge pull request #433 from odebeir/fix_rank_doc

DOC: Document 8 vs 16-bit input for Otsu / bilateral functions.
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
Change type to ssize_t for all index and size variables
Change type to ssize_t for all index and size variables
Change type to ssize_t for all index and size variables
Change type to ssize_t for all index and size variables
Rename Py_ssize_t to ssize_t for consistency within skimage
Change type to ssize_t for all index and size variables
Change type to ssize_t for all index and size variables
Change type to ssize_t for all index and size variables