Add support for mining license data using licensee

[andrew]

Adds licenses key to commits with data like:

[
  {:path=>"LICENSE.txt", :key=>"agpl-3.0", :confidence=>100}
]

May end up doing something more like the dependency data that shows the changes rather than license data on every commit, will ponder that before merging.

[andrew]

Looks like it doesn't like being ran on a branch in travis, hence the test failures 🙈