Improve commit data

[hyandell]

Currently oss-dashboard only pulls some of the relevant commit data.

• Would be good to also pull the author/committer GitHub logins when they exist.
• Good to also pull the email address of the Git author/committer.
• Would be nice to identify whether a commit is a merge from a pull request. Doesn't seem to be in the API though (outside of the message starting with "Merge pull request #x". Frustratingly the GitHub site appears to be able to connect these, presumably not via the message.

[hyandell]

First one is done now.

[jamesiri]

#142