Adding org.codehaus.groovy.transform.powerassert.ValueRecorder

The compiler used to compile src/test/java/**/*.groovy seems to produce
a reference to org.codehaus.groovy.transform.powerassert.ValueRecorder,
while our Groovy runtime appears to contain
org.codehaus.groovy.runtime.powerassert.ValueRecorder.

I suppose the proper fix is to somehow run Groovy 1.8 compiler,
but this fix adds the necessary code to the classpath.

test/pom.xml

@@ -155,6 +155,11 @@ THE SOFTWARE.
       <artifactId>findbugs-annotations</artifactId>
       <version>1.3.9-1</version>
     </dependency>
+    <dependency>
+      <groupId>org.codehaus.geb</groupId>
+      <artifactId>geb-implicit-assertions</artifactId>
+      <version>0.7.2</version>
+    </dependency>
   </dependencies>
 
   <build>