Adding radial background, keyframes and animation

I've been using this file in my projects with additional mixins which may help others:

1. Radial gradient backgrounds, with a normal gradient fallback for IE6-IE9.
2. CSS3 Keyframes
3. CSS3 Animation
transfered changes from scss to sass

1. Radial gradient backgrounds, with a normal gradient fallback for IE6-IE9.
2. CSS3 Keyframes
3. CSS3 Animation
Merge pull request #15 from domjtalbot/patch-1

Adding radial background, keyframes and animation