travis: Begin tagging docker containers with their version
travis: Begin tagging docker containers with their version

This will be necessary in future patches to ensure released versions
only use the corresponding minion containers.

LuiseV/quilt,tejasmanohar/quilt,ejj/quilt-dev,NetSys/quilt,kklin/kelda,kklin/quilt,kayousterhout/quilt,kayousterhout/quilt,kklin/quilt,quilt/quilt,kelda/kelda,quilt/quilt,ejj/quilt-dev,NetSys/quilt,ejj/quilt-dev,LuiseV/quilt,kayousterhout/quilt,kklin/kelda,NetSys/quilt,NetSys/quilt,kelda/kelda,tejasmanohar/quilt,tejasmanohar/quilt,LuiseV/quilt,LuiseV/quilt,kklin/kelda,kklin/quilt,kayousterhout/quilt,kklin/quilt,NetSys/quilt,quilt/quilt,quilt/quilt,kelda/kelda,LuiseV/quilt,ejj/quilt-dev,kklin/kelda,tejasmanohar/quilt,kelda/kelda