Update REAMDE to reflect:
* Disappearance of run_tempest.sh
* Tempest's use of stestr instead of testr
Also, add line about installation in development mode.
Change-Id: If927fe93efa3fa6a9d026f97880a21aff3114819
The docs can all fit into one easy-to-reference README. Do this.
Change-Id: I616a9bfb8446254d4f13de064328173ce5dd9b59
Depends-On: Ia00f32baee90594a4c91d872bbce83b9fdc927b7