nits and ripping out spec text for image,iframe,track etc.
ripping out what used to be section 4: Caching
SHA-1 is known-weak according to Wikipedia/NIST/Bruce Schneier. And we're killing it for CAs. Adding it to the spec.
change HTML resposne to JSON, because we don't do iframes for now
update CSP reference: pointing to 2 instead of 1.1