Update changes.txt for recent API changes

Change-Id: Ia65aa7e08c163acf30cd80eae608dc27c6250a2c
Add convenience RPC server classes

Rather than forcing all users of the server API to construct a
dispatcher and import a specific executor, add a convenience server
class e.g.

  server = eventlet.EventletRPCServer(transport, target, endpoints)

Note that openstack.common.messaging.eventlet need be the only public
module which has a dependency on eventlet. We can expose servers,
clients and anything else eventlet specific through this part of the
API.

Change-Id: I133e6d73fb0f60ea7f5e3b473a32dabc2f968084