In which we read requirement and documentation files relative to the setup.py location

This is required for installing packages from a subdirectory of a git repo.  I had to do make these changes to be able to install a package from a subdirectory, ala 

pip install -e "git+git@github.com:some-guy/some-repo.git#egg=a-package&subdirectory=a-directory"

I've got a repo which holds two packages in different directories off of the repo root.  This is also how to free yourself from the land of one-repo-on-package.

@mdorn