Improvements to MetricsFilter

* Added optional metering of HTTP status levels ("groups")
* Added ability to configure which specific status codes should be metered
update to play 2.2.2
update scala version
migrate to play 2.3.0
fix resolvers issue
update versions
Add support for Scala 2.11

* setup a cross build.
* upgrade specs2 dep to support 2.11
* add scala 2.11 to travis build.
update version
update version
fix version format