CSS3 Support, other optimisations

Hello,

Used Gritter on a project and thought I might thank you by adding support for css3 (with a fallback for IE7/8). Tested in Chrome and IE7:

* added css to style notifications without images (ok, 1 image, the cross would've taken more css than to base64 encode)
* added a support test for border radius
    * this will add a `.no-borderradius` class to body (same class as used by Modernizr)
* added .jshintrc; jshinted
* added License comment to css
* moved IE specific code into border-radius fallback
* removed `.gritter-top`, as `.gritter-item` is enough (I think it was a vestige from when the images were not yet sprited)
* removed _hoverState from JS as even IE7 handles `:hover`, as long as you have a proper doctype
* optimised images
* css is generated from sass

Also, I was wondering, why are you still supporting IE7?

HTH,
Armin