Update pom to fix the dependency issues.

- Update grpc-pubsub-v1 version 0.0.2
- Update grpc version to 0.12.0

gcloud-java-pubsub/pom.xml

@@ -26,7 +26,7 @@
     <dependency>
       <groupId>com.google.api.grpc</groupId>
       <artifactId>grpc-pubsub-v1</artifactId>
-      <version>0.0.1</version>
+      <version>0.0.0</version>
     </dependency>
     <dependency>
       <groupId>io.grpc</groupId>