MB-8745:  update READMEs for 2.2.0 release

Change-Id: I7a02b3e36f5bb63f39c7ba9fb70e6cd9e59c3d44
Reviewed-on: http://review.couchbase.org/28780
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>