The revision selector view lacked event handlers for touchscreen versions of

mousedown, mouseup, and mousemove 

(touchstart, touchend, touchmove, respectively), and required a bit

more padding in between handles for use on mobile devices.
This patch (presumably) fixes those issues.

Created a test suite for the Revision Selector View, but only contains

one test for the touchstart event as other event handlers proved too

difficult to test. The events that were beyond the authors ability

to test automatically were tested manually.