doc: Added dumpling to the sequence.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added Emperor upgrade.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Updated Emperor reference to 0.72.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
Merge branch 'master' of https://github.com/ceph/ceph