More minimal css code generation

[devth]

Nice work on this gem. I think it'd be great if it generated more minimal CSS like this:

.sprites.ratings { background: url('/images/sprites/ratings.png?1294942813') no-repeat; width: 60px; height: 11px; }
.sprites.ratings.ratings_star_0 { background-position: 0px 0px; }
.sprites.ratings.ratings_star_0_5 { background-position: 0px -11px; }
.sprites.ratings.ratings_star_1 { background-position: 0px -22px; }
.sprites.ratings.ratings_star_1_5 { background-position: 0px -33px; }
.sprites.ratings.ratings_star_2 { background-position: 0px -44px; }
.sprites.ratings.ratings_star_2_5 { background-position: 0px -55px; }
.sprites.ratings.ratings_star_3 { background-position: 0px -66px; }
.sprites.ratings.ratings_star_3_5 { background-position: 0px -77px; }
.sprites.ratings.ratings_star_4 { background-position: 0px -88px; }
.sprites.ratings.ratings_star_4_5 { background-position: 0px -99px; }