Fix CSS preproc to keep original CSS url quotes
Fix CSS preproc to keep original CSS url quotes

Otherwise this create a bug for fonts urls & IE (and it's just plain not nice to remove it when it was there in source)

http://paulirish.com/2009/bulletproof-font-face-implementation-syntax/
jwhitcraft/sinatra-assetpack,jwhitcraft/sinatra-assetpack,rstacruz/sinatra-assetpack,flywithmemsl/sinatra-assetpack,rstacruz/sinatra-assetpack,rstacruz/sinatra-assetpack,jwhitcraft/sinatra-assetpack,flywithmemsl/sinatra-assetpack,flywithmemsl/sinatra-assetpack