Added stopAfterTime & Wrap only once

Well I am sort of new at Github and this is my first Pull Request
I wanted to use this plugin but unfortunately it did not support a fixed time of Vibrate (when you just want the attention of the user).
So sort of made some changes. New at Javascript also so don't know if its optimized or not.
I believe you have already optimized the animation and all.

Hoping you can help me correct my mistakes.
Am using your code over here: http://ttt2-termvader.rhcloud.com/