Initial crop of feedback resulted in the following changes:

* Editor is dynamically sized to initial example to take care of browser issues.
* Warnings are parsed/managed like errors.
* Active line is highlighted only when editor is in focus.
Merge branch 'gh-pages' of github.com:graydon/rust-www into gh-pages
Fixed up duplicate commentary.
Merge pull request #28 from SergioBenitez/gh-pages

Initial crop of feedback changes