Test CSS3 gradient generator with Jasmine

Add tests around the CSS3 gradient generator

See https://github.com/dgalarza/CSS3Factory/pull/3 for test framework set up.

CC @acostanzo 
Moving it out into a `beforeEach` here would remove the details outside of the thing being tested making it harder to read. Later down the road, say line 10 without looking up to find a `beforeEach` without `swatch` being defined at the beginning it wouldn't be clear why we're testing ` "-o-linear-gradient(bottom, #FFFFFF 100%)",` etc..