Merge pull request #1 from derekadean/master

Adding gwt-dnd support
Made buttons display: block and changed drop controller

If buttons are not display: block, then the drop controller looks really
weird. Also, the drop controller is in the same package as the gwt-dnd
lib so I can call package protected methods. Probably not the best idea
ever.
Merge remote-tracking branch 'github/master'