Upgrade Scalaz 7.0.0-M8
Minor clean up: use collect
Explicitaly import scala-library so maven properly override libs that might still depend on 2.9.2, fix #971 in 1.4.X
Build own non synchronized ResponseBuilder, close #973
Upgrade AHC snapshot with fix for 225
Make XPath and JsonPath handle properly empty docs, use a Stream instead of a byte array, close #974
Upgrade Netty 3.6.3.Final, close #976
Introduce propagateSystemProperties, fix #977