Rename repo to pathspec

[pykong]

@cpburnz I feel this repo should be just called pathspec the same way you would install it from PyPI, as it is not the same as python-path-specification.

Minor detail, but it confused me.

[cpburnz]

@pykong I had wondered if the slight difference in the name would cause confusion. Thanks for letting me know. I'll look into Github's renaming capabilities.

[cpburnz]

I've renamed the project to python-pathspec because that best reflects it's a Python library named "pathspec".