Bump junit from 4.12 to 4.13

Bumps [junit](https://github.com/junit-team/junit4) from 4.12 to 4.13.
- [Release notes](https://github.com/junit-team/junit4/releases)
- [Changelog](https://github.com/junit-team/junit4/blob/master/doc/ReleaseNotes4.12.md)
- [Commits](junit-team/junit4@r4.12...r4.13)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

build.gradle

@@ -66,7 +66,7 @@ dependencies {
   compile group: 'commons-io', name: 'commons-io', version: '2.6'
   compile group: 'org.freemarker', name: 'freemarker', version: '2.3.29'
 
-  testCompile group: 'junit', name: 'junit', version: '4.12'
+  testCompile group: 'junit', name: 'junit', version: '4.13'
   testCompile group: 'org.hamcrest', name: 'hamcrest-library', version: '2.1'
   testCompile group: 'org.mockito', name: 'mockito-core', version: '3.0.0'
   testCompile group: 'org.skyscreamer', name: 'jsonassert', version: '1.5.0'