Bump Scala 2.11 version, SBT version, etc.

This commit upgrades the following versions:

 * Scala 2.11.2 -> 2.11.4
 * SBT 0.13.5 -> 0.13.7
 * ScalaTest 2.1.3 -> 2.2.1
 * ScalaCheck 1.11.3 -> 1.11.6
Merge pull request #328 from non/topic/version-updates

Bump Scala 2.11 version, SBT version, etc.
Merge remote-tracking branch 'origin/master' into topic/dist-maker-updates
Add convenience methods to Uniform, Gaussian, Exponential.

Previously you had to do:

    Uniform[Int].apply(1, 7)

...to dodge Uniform.apply's implicit parameter list.

This commit adds another apply method so you can just say:

    Uniform[Int](1, 7)