Add gz as application/octet-stream

What: jar pack200 files - http://docs.oracle.com/javase/tutorial/deployment/deploymentInDepth/reducingDownloadTime.html
Why: java browser plugin throws classnotfoundexception on the default content-type headers
Who needs it? Probably not that many people, but this is where the patch belongs and since node-mime is used through karma-runner, it'd be difficult to maintain a mime.define() in its code on all our CI servers.