Add labels

* labels display their shortest prefix which defines each rev
Fix lint problems
Merge branch 'master' of https://github.com/daleharvey/pouchdb into visualize-rev-tree
Revert pouch.alpha.js deletion

It needs to be deleted as it's quite old but it will get deleted
when I finish improving todo-list.
Merge pull request #479 from neojski/visualize-rev-tree

Visualize rev tree