[Buildbot] #3355: Create a nine migration guide

[Buildbot trac]

#3355: Create a nine migration guide
------------------------+---------------------
Reporter:  dustin       |       Owner:  dustin
    Type:  enhancement  |      Status:  new
Priority:  critical     |   Milestone:  0.9.0
 Version:               |  Resolution:
Keywords:  docs         |
------------------------+---------------------

Comment (by dustin):

 https://github.com/buildbot/buildbot/pull/1856

--
Ticket URL: <http://trac.buildbot.net/ticket/3355#comment:1>
Buildbot <http://buildbot.net/>
Buildbot: build/test automation