According to this post on SO OctoPress HTML escapes the output.
This fork fixes that OctoPress issue: https://gist.github.com/2925325
EDIT: The above fork is only needed on older versions of Octopress. Latest works with this gist
If you want a more comprehensive asset pipeline solution, you might consider Jekyll Asset Pipeline which will convert CoffeeScript, Sass, Less or any other language via an extension. It can also compress assets via Yahoo's YUI Compressor or Google's Closure Compiler.