Displaying all http/2 headers instead of parsing them.

I think that it makes more sense for someone using this to see the full
headers that the server returns. This was the status code and all the
headers (like CORS) that might be of interest while developing.
Extracting cache-control value to static method.
Updating Travis configuration.
Adding Netty snapshot repo.
Changes to reflect updates to Netty upstream.

HttpMethod.name() now returns AsciiString so we can simplify our code a
little.
Merge branch 'travis'