Move subsample files out of _subsample directory
Move extensions to be named __subsample
Update subsample unit test imports; regenerate C code from Cython
Fix broken subsample doctest
Fix formatting of module import in subsample unit tests
Move ssw wrapper code up one level, rename _ssw to _lib
Regenerate C code; update imports to ssw wrapper
Add __init__.py to _lib dir
Merge pull request #663 from jairideout/issue-658

Move python/cython code out of underscored directories