use version 2.28.2 of mockito to stay up to date

pom.xml

@@ -112,7 +112,7 @@
         <maven.javadoc.failOnError>false</maven.javadoc.failOnError>
 
         <!-- Test Dependencies: -->
-        <mockito.version>2.1.0</mockito.version>
+        <mockito.version>2.28.2</mockito.version>
         <groovy.version>1.8.6</groovy.version>
         <junit.version>4.8.2</junit.version>
         <hamcrest.version>2.0.0.0</hamcrest.version>