Removing safety section from idempotency topic.  Was duplicate text.
First pass at a copy edit. No technical changes.
Updated RFC 6585 status codes

428, 429, 431 and 511 are no longer drafts, they're published in RFC 6585
Also updated wikipedia references to reflect their change of status from draft to RFC
Merge branch 'master' of github.com:sadleb/RestApiTutorial.com into pull-requests
Fixed collapse toggler in httpstatuscodes #7
Merge branch 'master' of github.com:nobozo/RestApiTutorial.com into pull-requests
Merge branch 'master' of github.com:pnsantos/RestApiTutorial.com into pull-requests

Conflicts:
	httpstatuscodes.html