Build docker image in ci

.travis.yml

@@ -1,4 +1,6 @@
-language: node_js
+jobs:
+  include:
+    - language: node_js
       node_js:
         - "10"
       env:
@@ -19,3 +21,15 @@ install:
         - unzip -q test_data.zip -d test_data
       script:
         - xvfb-run --server-args="-screen 0 1024x768x24" npm test
+    - language: ruby
+      services:
+        - docker
+      before_install:
+        - docker build -t aktionskarten/tileserver-gl
+        - docker run -d -p 127.0.0.1:80:4567 aktionskarten/tileserver-gl /bin/sh -c "cd /root/sinatra; bundle exec foreman start;"
+        - docker ps -a
+        - docker run aktionskarten/tileserver-gl /bin/sh -c "cd /root/sinatra; bundle exec rake test"
+      script:
+        - bundle exec rake test
+        - echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
+        - docker push