Use a Scalaz construct that hasn't been removed in 7.1

See:

   https://github.com/scalaz/scalaz/commits/series/7.2.x/core/src/main/scala/scalaz/syntax/ApplySyntax.scala
   https://github.com/scalaz/scalaz/commit/14c5ba4943e57ce14a4070863353bc8259772b2b

This commit doesn't yet upgrade Scalaz to 7.1.x, but does allow us
to do so in our community build that include sbteclipse.
Merge pull request #223 from retronym/topic/scalaz-source-compat

Use a Scalaz construct that hasn't been removed in 7.1
Upgrade to sbt 0.13.6 version + syntax + the latest plugins