Actually fixing the angles in degrees

Right now the `fixAngle` function is broken, and the tests are just wrong.

1. This hack should be applied to any prefixed gradient, not only for `-webkit-`.
2. The actual formula is not the one you had here (see [this article](http://blogs.msdn.com/b/ie/archive/2012/06/25/unprefixed-css3-gradients-in-ie10.aspx) for example), so I replaced it and fixed the tests.

I didn't wrote in coffee before, so you could fix any codestyle issues I have :)