Fix several MS compiler warnings.
Minor cleanup in dtypestring parsing.
Add ptrdiff_t type to Cython.
ptrdif_t test
Merge pull request #231 from joshayers/ms_compiler_warnings

Fix several MS compiler warnings.
Document cythonize accepts Extension arguments.
Update compilation instructions.
Merge pull request #234 from wichert/doc-compilation

Document cythonize accepts Extension arguments.
Even more clarification on cythonize().