Introducing the CSP Fixer

@devoncarew

Devon: sorry, a couple of unrelated trivial changes have crept in.

I should also add tests.

Also note that I deliberately exposed the feature only in the form of an explicit action. I didn't want to build it into the Bower install/update sequence or anything like that because it's too early and too risky.

@jmesserly for FYI. It looks like the html5lib dom is adding in `<html>`, `<head>`, and `<body>` tags when creating text from the parsed DOM. I'm not sure if this is expected or not -