update frameworks sample dependency versions (#458)

Author: tangiel

appengine/endpoints-frameworks-v2/backend/pom.xml

@@ -31,8 +31,8 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
-        <endpoints.framework.version>2.0.0-beta.9</endpoints.framework.version>
-        <endpoints.management.version>1.0.0-beta.11</endpoints.management.version>
+        <endpoints.framework.version>2.0.0-beta.12</endpoints.framework.version>
+        <endpoints.management.version>1.0.0-beta.12</endpoints.management.version>
 
         <endpoints.project.id>YOUR_PROJECT_ID</endpoints.project.id>
         <maven.compiler.target>1.7</maven.compiler.target>