Have CI push Docker image

.travis.yml

@@ -6,10 +6,19 @@ rvm:
   - 2.5
 
 addons:
-  postgresql: "9.6"
+  postgresql: 10
 before_install:
   - "psql -c 'create database frankfurter_test;' -U postgres"
 
-bundler_args: "--without development"
+services:
+  - docker
+
+bundler_args: "--without development test"
 env:
   - APP_ENV=test
+
+deploy:
+  provider: script
+  script: bash bin/docker_push
+  on:
+    branch: master

bin/docker_push

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
+docker build -t "$DOCKER_USERNAME/frankfurter" .
+docker push "$DOCKER_USERNAME/frankfurter"