Refer new branches to an existing baseline

[raboof]

though that existing baseline is now hard-coded as '2' :)

[skwakman]

Thanks for the addition @raboof . I've recently fixed the flaky tests on master (was a memory issue on travisCI by the looks of it), so tests are now failing with a good reason. It seems that the branch.clj file is missing. Could you add that one to this PR?

[raboof]

@skwakman I merged in master and think I fixed a couple of things, but still see test failures - not completely sure how to read them :)

[raboof]

Hmm, I suppose still missing are:

• default to 'master' when no branch name is provided (might be causing the failing tests)
• select the right baseline instead of hardcoding '2' :)
• add tests :)