Better handle socket closing with loop handlers

We now read from the socket to be able to detect errors or TCP close
events, and buffer the data if any. Once the data receive goes over
a certain limit, which defaults to 5000 bytes, we simply close the
connection with an {error, overflow} reason.
Add a few directions in the REST chapter in the guide

This is obviously not proper documentation. We will properly document
it when the API stabilizes.
Add a REST point on the roadmap
Merge branch 'static_doc' of git://github.com/acammack/cowboy
Add a REST example that streams its response