Changed to older version of checkstyle to be compatible with JDK 1.7
Changed to older version of checkstyle to be compatible with JDK 1.7

GoogleCloudPlatform/pubsub,kamalaboulhosn/pubsub,GoogleCloudPlatform/pubsub,kamalaboulhosn/pubsub,kamalaboulhosn/pubsub,kamalaboulhosn/pubsub,GoogleCloudPlatform/pubsub,GoogleCloudPlatform/pubsub,GoogleCloudPlatform/pubsub,kamalaboulhosn/pubsub