Add new parameter to release job: SCALA_BINARY_VER

Otherwise, the build for privately published build of Scalacheck
[fails](https://scala-webapps.epfl.ch/jenkins/view/scala-release-2.11.x/job/scala-release-2.11.x/54/console) for binary-compatible releases (ie, non-RCs) with:

    unresolved dependency: org.scala-lang.modules#scala-parser-combinators_2.11.0;1.0.1: not found