added a build file.
added a build file.

This allows this project to be build independently from jenkins.

kmbarry1/appengine-sidecars-docker,oierw/appengine-sidecars-docker,oierw/appengine-sidecars-docker,kmbarry1/appengine-sidecars-docker,GoogleCloudPlatform/appengine-sidecars-docker,oierw/appengine-sidecars-docker,kmbarry1/appengine-sidecars-docker,GoogleCloudPlatform/appengine-sidecars-docker,oierw/appengine-sidecars-docker,kmbarry1/appengine-sidecars-docker