Test building and running application images

Adds a cucumber/aruba based testsuite that tests building and running Ruby, Node.JS, Clojure, Python, Java, Gradle, Grails, Scala, Play, PHP and Go applications.

Also includes a [Wercker](http://www.wercker.com) configuration that can be used to run these tests on commit/for pull requests. Didn't use Travis-CI since running docker by way of User Mode Linux was pretty flaky an slow.