Add setup.py for pip install

This lets users install directly from github with pip, either by running
it directly:

    pip install -e git+https://github.com/REPO/gevent_openssl#egg=gevent_openssl

...or by adding -e git+https://github.com/REPO/gevent_openssl#egg=gevent_openssl
to a requirements file.
TEMP: point back at the current repository

This will keep things running while we're waiting to merge a pull
request to the original repository.
Merge pull request #1 from demiurgestudios/master

Add setup.py for pip install