Merge pull request #13 from wregab/master

Thanks @wregab for the PR!
P19Spec - new tests
Specs2 2.3 upgrade + shorter (simpler?) way to describe resolvers
Replace imports and extends following http://etorreborre.github.io/specs2/guide/org.specs2.guide.QuickStart.html
org.specs2:specs2 2.3.1