Use github auth for git clones

Use github oauth token or a github user and password for git clones.

Send config through to git clone so we can get the auth settings.
Only use auth for cloning if the PR is private
Fix tests with new extra argument for clone_or_update
Add MANIFEST.in

So the requirements.txt, Readme, and License, will be included for
`sdist`

https://docs.python.org/2/distutils/sourcedist.html#the-manifest-in-template
Merge pull request #1 from zoidbergwill/master

Use Github auth for git clones if the PR is private