* Reuse the images from the repository in README
* Shrink the images to 800-1000px
* Fix incorrect sectioning, typos, missing info etc. on ReadTheDocs
* Add a tutorial step about the --abort-on-sla-failure feature
* Move Rally deployment engines to a separate tutorial step
* rally use deployment -> rally deployment use
Change-Id: Id5f492e40a041aa3308e9faa21b833220415323d