Support for devices with gyro

[LinusU]

Hi @lhagan,

I forked your repo and turned it into a generic javascript plugin instead of depending on jQuery. It now emits a deviceshake-event on the window object.

I also added support for better accuracy on devices with gyro which you might want to copy from me, see: https://github.com/LinusU/deviceshake.js/blob/ae4c29b415b21034c5ec411eb59269fac665f71b/deviceshake.js#L48-63

Thanks for a great library! Linus Unnebäck