Resolve JUnit 4.10 vs. 4.11 classpath conflict

ethereumj-core depends on elements specific to the JUnit 4.11 API, but (for
reasons that can only be assumed dubious) json-simple:1.1.1 transitively
includes JUnit 4.10. At the command line, Gradle handles this cleanly,
and gives ethereumj-core's direct dependence on 4.11 the precedence it
deserves. However, IDEA gets confused and gives 4.10 precedence. This
change explicitly excludes the transitive dependency from
json-simple->junit:4.10, eliminating the issue completely.

ethereumj-core/build.gradle

@@ -59,7 +59,6 @@ dependencies {
     compile "org.slf4j:slf4j-log4j12:${slf4jVersion}" // TODO: runtime scope
     compile "log4j:log4j:${log4jVersion}"
     compile "log4j:apache-log4j-extras:${log4jVersion}"
-    compile "com.googlecode.json-simple:json-simple:1.1.1"
     compile "org.codehaus.jackson:jackson-mapper-asl:1.9.13"
     compile "com.google.code.findbugs:jsr305:3.0.0"
     compile "com.fasterxml.jackson.core:jackson-databind:2.2.0"
@@ -71,6 +70,9 @@ dependencies {
     compile "org.hibernate:hibernate-core:${hibernateVersion}"
     compile "org.hibernate:hibernate-entitymanager:${hibernateVersion}"
     compile "commons-dbcp:commons-dbcp:1.4"
+    compile("com.googlecode.json-simple:json-simple:1.1.1") {
+        exclude group:'junit', module:'junit'
+    }
     testCompile "junit:junit:${junitVersion}"
     testCompile "org.springframework:spring-test:${springVersion}"
 }

ethereumj-core/src/test/java/test/ethereum/vm/VMTest.java

@@ -1,6 +1,5 @@
 package test.ethereum.vm;
 
-import junit.framework.Assert;
 import org.ethereum.facade.Repository;
 import org.ethereum.util.ByteUtil;
 import org.ethereum.vm.*;