Updated HTTP/1.1 reference.
Merge branch 'master' of https://github.com/http2/http2-spec
Update examples.

Add some simple examples for each header representation.
Modify request/response examples to show more features.
Solves #313 (break down examples into smaller artwork fragments).
Solves #321 (use example host names).
Solves #297 (all suggested example are covered).