Make DPickler a pure abstract trait

- Removes macro invocation in DPickler
- This is part of an effort to separate the pickling API from
  the macro implementation
Merge pull request #132 from phaller/topic/modularize-api

Make DPickler a pure abstract trait
Travis: build using Scala 2.11.2
Merge pull request #149 from phaller/topic/travis-scala-version

Travis: build using Scala 2.11.2
Adding static-only switch to pickling
Adds ability to test for failed compilation + 1 static only test