Push all images upon release tag

[alexellis]

Expected Behaviour

All images should be pushed with their version numbers as per stack.yml when doing a release build

Current Behaviour

This is semi-manual and can lead to some missing versions.

Possible Solution

Update travis.yml to include each stack.yml (and equivalent name) for build/push.

edge-router / edge-auth should perhaps use the git tag version rather than a manually incremented version. This should make keeping in-sync easier between Docker image versions and deployment YAML files.

[alexellis]

@LucasRoesler could you look into this one? Since you've not been that close to OFC yet, your external view would be appreciated.