CSP: Porting from Respec to Bikeshed.

Bikeshed gives us much better ability to interlink with other
specifications, and cleaner code across the board. It also means we can
easily steal the CSSWG's stylesheet, which is a significant improvement
over what we've been using.
Merge pull request #19 from w3c/bikeshed

CSP: Porting from Respec to Bikeshed.
CSP: Updating with the new URL.
CSP: Dropping section numbers for conformance section.
CSP: Fixing the URL and mixed-content error.
CSP: Document proposed solution to redirect-target path leakage.

In a nutshell, this proposal patches the matching algorithm to ignore
the path component in source expressions if the URL being matched is the
result of an HTTP redirect. Since these requests will now be host/scheme
based, we still get reasonable protection by limiting resources to
allowed origins after a redirect, while not allowing malicious parties
to brute-force paths through cleverness.