Bump Junit Runner to 1.0.12

Testing Done:
CI at https://travis-ci.org/pantsbuild/pants/builds/144304371

Bugs closed: 3661

Reviewed at https://rbcommons.com/s/twitter/r/4072/

src/python/pants/backend/jvm/tasks/junit_run.py

@@ -115,7 +115,7 @@ def register_options(cls, register):
     cls.register_jvm_tool(register,
                           'junit',
                           classpath=[
-                            JarDependency(org='org.pantsbuild', name='junit-runner', rev='1.0.11'),
+                            JarDependency(org='org.pantsbuild', name='junit-runner', rev='1.0.12'),
                           ],
                           main=JUnitRun._MAIN,
                           # TODO(John Sirois): Investigate how much less we can get away with.