Update PowerMock 1.5.1->1.5.5

https://raw.githubusercontent.com/jayway/powermock/master/changelog.txt

Change-Id: Ib9005f6cc711152b5941b3d0bf8b68dae52d978a
diff --git a/pom.xml b/pom.xml
index 29b8520..3f667a6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -30,7 +30,7 @@
   </repositories>
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <powermock.version>1.5.1</powermock.version>
+    <powermock.version>1.5.5</powermock.version>
     <restlet.version>2.1.4</restlet.version>
     <cobertura-maven-plugin.version>2.6</cobertura-maven-plugin.version>
     <!-- Following 2 findbugs version needs to be updated in sync to match the