Update bookmarklet to use rawgit.com

raw.github.com adds 'X-Content-Type-Options: nosniff' headers. This causes the browser to refuse to execute JS because it's served with 'text/plain' content type and "nosniff" turns on strong MIME type checking.

rawgit.com is a service that fixes this by proxying raw.github.com and sending correct MIME types for files.