Document the clownlist better

Summary: Looks like I can unclownlist mustache in the near future, but not the others :'(

Reviewed By: @JoelMarcey

Differential Revision: D1394928
Clownlist a bad assetic test, re-record

Summary: Additionally, jpegtran has always been skipped as we don't have that binary available on our systems.

Reviewed By: @JoelMarcey

Differential Revision: D1394898