Narrative updates

* update dev environment slide
* add jobs launched graph to project gating slide
* rename trunk gating -> project gating
* replace several gerrit/lp slides with one large
  gerrit slide
* add gerrit diff slide
* remove lp blueprint integration slide
* replaced process flow text with diagram
* removed states of a patch slide
* removed typos of gerrit triggers slide
* removed extra path elements in git-review example
* move zuul status slide to replace jenkins in "everything is automated"
* update README.rst to match

Change-Id: I3f93953bf64f0b3e7735821d8bcb1bab5fffa7d9