Bumping dependency versions

 * scodec-core -> 1.3.0
 * spec2 -> 2.4.4

The need for a new resolver for «scalaz-stream» is disapointing. When using
the sbt graph plugin from «virtualvoid.net», no transitive dependency on
«scalaz-stream» show up. As previously I didn't have to had any resolver for
this, I spent too much time to figure out what was happening!

The codec part is still OK, but the protocol part is completely broken.