Update build and test, enable Scala-2.11

Hi,

Here is some cleanup and update of the build and test infrastructure

- Enable building with Scala-2.11
- Drop support for Scala-2.9 - akka-2.3 is not available
- Use sbt-0.13.5 with sbt-osgi 0.7.0. The old version is not available for Scala-2.11
- ported akka tests from Spec to scalatest framework (spec is deprecated long time ago and is not available for Scala-2.11 )

You can ignore the changes in TupleSerializationTest.scala - my editor converted the line endings in unix style. 

Some more work need to be done:

- compiling JUnit based test in one pass with scalatest based ones crashes the compiler, it complains of multiple definitions of Nil found. I was hoping that this was a bug of "spec"

- osgi definitions and versions should be fixed but I do not know what they mean.