Lock ZenTest to ~> 4.5.0 for JRuby on NUBIC's CI server.
Lock ZenTest to ~> 4.5.0 for JRuby on NUBIC's CI server.

JRuby 1.6.4 ships with a version of RubyGems that's too old for ZenTest
~> 4.6.0, and we have 1.6.4 on the CI server.

NUBIC/castanet