Scala 2.11 compatible dependencies

 - Bump minor versions of Scalaz and Scalacheck
 - Exclude unwanted transitive depenencies of scala-compiler.
   This is a temporary measure that will not be needed after 2.11.0-M8
   as the compiler will no longer depend on the prior version of
   xml and parser-combinators.
 - Conditionally depend on an snapshot of Shapeless (must be build
   locally, I've asked Miles to publish a stable version)