Travis-CI: docker image as build environment
<p>In <strong>Travis CI</strong> is it possible to run the build process from inside a docker container? </p>

<p>In <a href="http://docs.gitlab.com/ce/ci/docker/using_docker_images.html" rel="noreferrer"><strong>GitLab CI</strong></a> this is the default. We can simply define the image in <code>.gitlab-ci.yml</code> then all the build/test/deploy will run inside that container. However, Travis seems to have <a href="https://docs.travis-ci.com/user/docker/" rel="noreferrer">totally different</a> view about docker usage. How can I achieve a similar behavior in Travis? </p>