Remove compile-scoped junit dependency.

This avoids having junit classes showing up in the assembly jar.
I verified that only test classes in the jtransforms package
use junit.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #794 from vanzin/junit-dep-exclusion and squashes the following commits:

274e1c2 [Marcelo Vanzin] Remove junit from assembly in sbt build also.
ad950be [Marcelo Vanzin] Remove compile-scoped junit dependency.

mllib/pom.xml

@@ -50,6 +50,14 @@
       <groupId>org.scalanlp</groupId>
       <artifactId>breeze_${scala.binary.version}</artifactId>
       <version>0.7</version>
+      <exclusions>
+        <!-- This is included as a compile-scoped dependency by jtransforms, which is
+             a dependency of breeze. -->
+        <exclusion>
+          <groupId>junit</groupId>
+          <artifactId>junit</artifactId>
+        </exclusion>
+      </exclusions>
     </dependency>
     <dependency>
       <groupId>org.scalatest</groupId>

project/SparkBuild.scala

@@ -322,6 +322,7 @@ object SparkBuild extends Build {
   val excludeJruby = ExclusionRule(organization = "org.jruby")
   val excludeThrift = ExclusionRule(organization = "org.apache.thrift")
   val excludeServletApi = ExclusionRule(organization = "javax.servlet", artifact = "servlet-api")
+  val excludeJUnit = ExclusionRule(organization = "junit")
 
   def sparkPreviousArtifact(id: String, organization: String = "org.apache.spark",
       version: String = "1.0.0", crossVersion: String = "2.10"): Option[sbt.ModuleID] = {
@@ -466,7 +467,7 @@ object SparkBuild extends Build {
     previousArtifact := sparkPreviousArtifact("spark-mllib"),
     libraryDependencies ++= Seq(
       "org.jblas" % "jblas" % jblasVersion,
-      "org.scalanlp" %% "breeze" % "0.7"
+      "org.scalanlp" %% "breeze" % "0.7" excludeAll(excludeJUnit)
     )
   )