Fix touch handling when using jQuery

When using jQuery, events seem to get "fixed" to work around some browser bugs, but this doesn't work perfectly for touches. See (http://www.the-xavi.com/articles/trouble-with-touch-events-jquery) for more details. This meant that if someone used orbit with jQuery rather than zepto, touch handling would be broken due to e.touches being undefined.

This fixes that case.
Merge pull request #1775 from peterbrook/fix-orbit

Fix touch handling when using jQuery