Upgrade to JUnit 4.12

- includes @Parameters attribute that allows you to define a template for names of tests, making the test output far easier to follow.

prime-factors/build.gradle

@@ -7,5 +7,5 @@ repositories {
 }
 
 dependencies {
-  testCompile "junit:junit:4.10"
+  testCompile "junit:junit:4.12"
 }