add yui-compressor to tools/
compress css with yui-compressor before merging it
delete unused files
compress vm/*.css -> vm/vm.css & use vm/vm.css in vm
compress each file in css/ & stylesheets/structure/. make dev server consistent with production (file names of compressed css were different)
Merge pull request #243 from srinivasupadhya/compress-css

Compress css using yui-compressor
closure-compiler requires JDK 7. moving to yui-compressor.
moving rake task to use yui-compressor.