Add REST diagram for OPTIONS method
Add more REST diagrams
Add variances to the conneg diagram
Add REST diagram for the part about conditional requests
Add REST diagram for GET and HEAD
Add REST diagram for DELETE method
Add REST diagram for PUT/POST/PATCH
Add more details about the 304 in cond diagram
Add a stub chapter with all the REST flowcharts

The detailed explanations will be written at a later time.
Add a missing "true" label
Write the guide chapter rest_flowcharts explaining the diagrams
Add a multipart intro chapter to the guide
Wrap-up the user guide
Cowboy works fine under 17.1
Document the HTTP status codes Cowboy may send in the manual

422 is left out as it's soon to be replaced by 400.
Fix cowboy_spdy parse frame
Update erlang.mk and update paths to start the release

Fixes a couple invalid instructions at the same time.
Fix typo
Roadmap for Cowboy 2.0
Forgot a todo in the ROADMAP