Add template keyword block for outputting code without changes

[benweatherman]

Using javascript templates is tricky because it often requires you to use similar syntax to Tornado templates. While you can use the {{! and {{% syntax, this is often pretty cumbersome for large chunks of javascript templates. I propose we have a verbatim/raw/cdata keyword that would output my template code unchanged.

For more information, see this thread: http://groups.google.com/group/python-tornado/browse_thread/thread/8d0383a76324e0a6/741315ab35621caa?lnk=gst&q=templates#

[benweatherman]

Well I'm a pull request dummy. This is now issue #318.