Docker based test
Created by: yookoala
Instead of testing in Travis system image natively, this PR changed Travis config to test in Docker environment. ibus-cangjie
is tested against stock Python, system packages and properly-installed pycangjie.
The testing environment is build on Ubuntu 16.04 Docker image. Each layer of the testing environment is based on the latest source in the stack, properly build and tested, then pushed to Dockerhub.
Fix #78 (closed).