Support for devices with both a mouse and touch events

At the moment backbone.touch doesn't play nicely with devices that have both a touch event and a mouse available. I believe this change will help to alleviate this problem, however I don't have many devices to test on. Can you take a look and see if you think this will help?

My issue has occurred within my application with users who have a Chromebook Pixel not being able to click on any links with the mouse pad. I don't have a Chromebook Pixel to test on either, but I will be pushing out this change to my users to see if it fixes it.

Cheers!