Remove support for sliding around star ratings (bug 978046)

https://bugzilla.mozilla.org/show_bug.cgi?id=978046

Currently you can swipe your finger back and forth across the stars to change your rating but it's pretty janky because the `click` event gets triggered on the first touch which causes the text area to be selected. This also drops an error in the console on 'touchend' since there are no touchs.

Before
![swipe-stars mp4](https://cloud.githubusercontent.com/assets/211578/3458976/403d9986-0207-11e4-9149-d6ef34d5260c.gif)

After
![no-swipe-stars mp4](https://cloud.githubusercontent.com/assets/211578/3459057/489cdfd2-0208-11e4-9fb8-5f441c60bfb7.gif)