Add docker runtime image (#21)

Closes #17

.travis.yml

@@ -2,13 +2,9 @@ sudo: required
 services:
   - docker
 install:
-  - curl -fsSL https://github.com/docker/compose/releases/download/1.12.0/docker-compose-`uname -s`-`uname -m` > docker-compose
-  - chmod +x docker-compose
-  - sudo mv docker-compose /usr/local/bin/docker-compose
+  - docker version
   - docker-compose version
-  - docker-compose pull
-  - docker-compose build
-  - docker-compose up -d
-  - docker-compose run dbmate go version
 script:
   - make
+  - docker build -t dbmate .
+  - docker run --rm dbmate --help