Add continuous delivery of images to DockerHub

.travis.yml

@@ -1,7 +1,15 @@
 language: python
+services:
+  - docker
 python:
   - "3.6"
 install:
   - pip install -r requirements.txt
 script:
   - tools/ci.sh
+deploy:
+  - provider: script
+    script: tools/cd.sh
+    on:
+      repo: chakki-works/doccano
+      tags: true

tools/cd.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+
+if [[ -z "${DOCKER_USERNAME}" ]]; then echo "Missing DOCKER_USERNAME environment variable" >&2; exit 1; fi
+if [[ -z "${DOCKER_PASSWORD}" ]]; then echo "Missing DOCKER_PASSWORD environment variable" >&2; exit 1; fi
+if [[ -z "${TRAVIS_TAG}" ]]; then echo "Missing TRAVIS_TAG environment variable" >&2; exit 1; fi
+
+set -o errexit
+
+docker build -t "${DOCKER_USERNAME}/doccano:latest" .
+docker build -t "${DOCKER_USERNAME}/doccano:${TRAVIS_TAG}" .
+
+echo "${DOCKER_PASSWORD}" | docker login --username "${DOCKER_USERNAME}" --password-stdin
+
+docker push "${DOCKER_USERNAME}/doccano:latest"
+docker push "${DOCKER_USERNAME}/doccano:${TRAVIS_TAG}"