Bump mockito-core from 2.27.0 to 2.28.2

Bumps [mockito-core](https://github.com/mockito/mockito) from 2.27.0 to 2.28.2.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v2.27.0...v2.28.2)

build.gradle

@@ -67,7 +67,7 @@ dependencies {
     }
 
     testCompile group: 'junit', name: 'junit', version: '4.12'
-    testCompile group: 'org.mockito', name: 'mockito-core', version: '2.27.0'
+    testCompile group: 'org.mockito', name: 'mockito-core', version: '2.28.2'
 }
 
 apply from: 'gradle/tests.gradle'