io: improve ChannelRegistryImpl.select task
io: upgrade to Akka IO as of 2013-05-01
Merge branch 'akka-io-update'

Conflicts:
	spray-io/src/main/scala/akka/io/SelectionHandler.scala
	spray-io/src/main/scala/akka/io/Tcp.scala
	spray-io/src/main/scala/akka/io/TcpConnection.scala
	spray-io/src/main/scala/akka/io/TcpListener.scala
	spray-io/src/main/scala/akka/io/UdpListener.scala
http: add missing equals/hashcode override to MessageChunk
can: add two more tests
can: make warning log messages on illegal headers configurable
Json4s native and jackson support