Merge pull request #29 from herimedia/token-auth

Add OAuth2 token authentication to GitHub API client

Thanks to Niels Ganser for the nice patch. Users need to the following
command to obtain an OAuth token:

`curl -i -u USERNAME -X POST -d '{"scopes":["public_repo"]}' https://api.github.com/authorizations`

Signed-off-by: Patrick Wagstrom <patrick@wagstrom.net>