Add override for python-neutronclient.
Update URL to point to PyPI

PyPI has a universal wheel available which is fairly explicit.
Remove ipaddress, pyephem, and pystache overrides

These overrides are stale and can be removed.
Merge pull request #65 from vaibhavsagar/stale-overrides

Remove ipaddress, pyephem, and pystache overrides
Merge pull request #64 from vaibhavsagar/neutronclient

Add override for python-neutronclient