Refactor setupDragZoom onto the DragInteraction and move it out of top level namespace.
Add dragzoom-quicktest.
Close #489
Update built files
Merge branch 'master' into refactor-dragzoom

Conflicts:
	plottable.min.js
	plottable.zip
Update built files
Merge pull request #494 from palantir/refactor-dragzoom

Refactor dragzoom