Version 2.3-M2

Updating Scala to 2.11.0-M7 fix tests/compilation

Version 2.2.3

Bumping version to v2.2.3

Version 2.3-M1

Version 2.2.2

Updating Scala to 2.11.0-M5, ScalaTest to 2.0.M7 and fix tests/compil…

…ation

Version 2.2.1

Version 2.2.0

add verification of ping-pong chains

- basic principle is that if we get a reply of type T1 and our channels
  allow us to reply to such a message with type T2, then the target
  needs to support that as well, and so on.
- due to this, forwarding will have to be restricted; but it might well
  be that forwarding will not be completely safe in any case