Bump powermock to 1.5.6 that support java 8

pom.xml

@@ -152,18 +152,18 @@ THE SOFTWARE.
       <dependency>
         <groupId>org.mockito</groupId>
         <artifactId>mockito-core</artifactId>
-        <version>1.8.5</version>
+        <version>1.9.5</version>
       </dependency>
       
       <dependency>
         <groupId>org.powermock</groupId>
         <artifactId>powermock-module-junit4</artifactId>
-        <version>1.4.10</version>
+        <version>1.5.6</version>
       </dependency>
       <dependency>
         <groupId>org.powermock</groupId>
         <artifactId>powermock-api-mockito</artifactId>
-        <version>1.4.10</version>
+        <version>1.5.6</version>
       </dependency>
 
       <dependency>