Draw brush on selection.
This draws the brush but does not yet trigger the events. The problem was that
the selection needs to be a d3 selection, not just a selector string.
Upgrade to d3 v3
Fix #17.

The brush is now draw correctly and events are triggered when given an extent.
The events are called manually instead of call brush with a selection. Not sure
why I need to do this the documentation indicates that I shouldn't have to.