[maven-release-plugin] prepare release gcloud-maven-plugin-0.9.56.v20150418
[maven-release-plugin] prepare release gcloud-maven-plugin-0.9.56.v20150418

ludoch/gcloud-maven-plugin,GoogleCloudPlatform/gcloud-maven-plugin,GoogleCloudPlatform/gcloud-maven-plugin,GoogleCloudPlatform/gcloud-maven-plugin