Fixes toCSS bug that generated redundant optimized @keyframes.

Squashed commit of the following:

commit f6fe52a30b272b24b1546a0c3ccc337c24e988b1
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 13 20:21:56 2013 -0700

    Builds v.0.14.4.

commit 162bf5a1f07c71df959a0005a2479dfd78846924
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 13 16:06:43 2013 -0700

    Adds potential fix for redundancy bug.

commit 86b183d89e4dd20e0a9d9d77c4bfe6472b02037d
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Sat Jul 13 15:38:08 2013 -0700

    Adds failing unit test.