Update junit runner to 1.0.15 to get java 7 compatibility

The junit-runner 1.0.15 jar should now be java 7 compatible.

Also set the platform of the scala and javac tool to java7 for the next time those are published.

Testing Done:
Build green at https://travis-ci.org/pantsbuild/pants/builds/168588698

Also tested this jar in our Java repo under Java 7 and it works.

Bugs closed: 3986

Reviewed at https://rbcommons.com/s/twitter/r/4324/

src/python/pants/backend/jvm/subsystems/junit.py

@@ -21,7 +21,7 @@ class JUnit(JvmToolMixin, Subsystem):
   RUNNER_MAIN = 'org.pantsbuild.tools.junit.ConsoleRunner'
 
   _LIBRARY_JAR = JarDependency(org='junit', name='junit', rev=LIBRARY_REV)
-  _RUNNER_JAR = JarDependency(org='org.pantsbuild', name='junit-runner', rev='1.0.14')
+  _RUNNER_JAR = JarDependency(org='org.pantsbuild', name='junit-runner', rev='1.0.15')
 
   @classmethod
   def register_options(cls, register):

src/scala/org/pantsbuild/zinc/BUILD

@@ -15,4 +15,5 @@ scala_library(
   ],
   sources=globs('*.scala'),
   strict_deps=True,
+  platform='java7',
 )

src/scala/org/pantsbuild/zinc/cache/BUILD

@@ -11,4 +11,5 @@ scala_library(
   ],
   sources=globs('*.scala'),
   strict_deps=True,
+  platform='java7',
 )

src/scala/org/pantsbuild/zinc/logging/BUILD

@@ -10,4 +10,5 @@ scala_library(
   ],
   sources=globs('*.scala'),
   strict_deps=True,
+  platform='java7',
 )

src/scala/sbt/compiler/javac/BUILD

@@ -9,4 +9,5 @@ scala_library(
     '3rdparty/jvm/com/typesafe/sbt:incremental-compiler',
   ],
   sources=globs('*.scala'),
+  platform='java7',
 )

src/scala/sbt/inc/BUILD

@@ -9,4 +9,5 @@ scala_library(
     '3rdparty/jvm/com/typesafe/sbt:incremental-compiler',
   ],
   sources=globs('*.scala'),
+  platform='java7',
 )