Don't load the macro-paradise plugin under 2.11

The required functionality (quasiquites) is now part of the normal
compiler.

This has the nice effect of avoiding bugs like:

  https://github.com/scalamacros/paradise/issues/7
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.