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 
@dgalarza I always found it painfully repetitive and error prone to write out all of those prefixes. Would it be bad practice to have some sort of spec helper to generate an array with prefixed and suffixed values?