Added guts to be able to add ?compressed=1 to the URL and cause loading the compressed version instead.

TBR=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/7232044

git-svn-id: http://blockly.googlecode.com/svn/trunk@600 c400ca83-b69d-9dd7-9705-49c6b8615e23