Improves hover detail placement when space is tight

The layout error for hover detail elements is now checked for both
left and right alignment.  Then the alignment with the least error is
used.
Merge pull request #332 from kungfubanana/better-hover-detail-placement

Improves hover detail placement when space is tight
update built libs
Update README.md
excise Rickshaw.Graph.Unstacker and allow for consumers to pre-stack if they like; fixes #333
Merge branch 'master' of github.com:shutterstock/rickshaw