Merge pull request #56 from samoht/master

prepare the release
Merge pull request #57 from samoht/master

clean-up before the release
Merge pull request #58 from samoht/master

More API clean-ups
Better support for random tag name in the Git backend

No need to prefix all the tag names by refs/heads anymore
Diplay some nice graphs when asking the HTTP server to dump the database

This does not scale very well, but we could try to adapt something like http://cs.brown.edu/people/jcmace/d3/graph.html?id=small.json later (the source is somewhere in https://github.com/brownsys/X-Trace/tree/master/src/main/resources/webui/html/interactive)