Switch to my own fork of scala-io.

My fork:
  1. disables building of scaladoc docs (due to regression in scaladoc)
  2. adds dependency on scala-parser-combinators
Lock particular version of specs2

Latest master of specs2 breaks on Scala master due to
https://github.com/etorreborre/specs2/commit/2f4aca25c66e1f5640b32642208178d46888dfec