travis: automate pushing images when building from tag

.travis.yml

@@ -1,3 +1,4 @@
+---
 language: go
 
 go:
@@ -18,11 +19,22 @@ services:
 
 jobs:
   include:
-    - stage: Integration Tests
+    - name: Integration Tests
+      stage: test
       before_script:
         - curl -Lo kind https://github.com/kubernetes-sigs/kind/releases/download/v0.7.0/kind-linux-amd64 && chmod +x kind && sudo mv kind /usr/local/bin/
         - kind create cluster --config test/e2e/kind-config/kind-config.yaml
       script:
         - VERSION=local make container
         - kind load docker-image quay.io/brancz/kube-rbac-proxy:local
         - make test-e2e
+    - name: Push container images
+      stage: push-docker-image
+      script:
+        - "echo ${QUAY_PASSWORD} | docker login -u ${QUAY_USERNAME} --password-stdin quay.io"
+        - VERSION=$TRAVIS_TAG make push
+
+stages:
+  - name: test
+  - name: push-docker-image
+    if: (type != pull_request) AND (tag =~ ^v)