Add Ubuntu 16.04 to Travis test environments.

Author: geerlingguy

.travis.yml

@@ -10,6 +10,10 @@ env:
     version: latest
     init: /usr/lib/systemd/systemd
     run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
+  - repository: geerlingguy/docker-ubuntu1604-ansible
+    version: latest
+    init: /lib/systemd/systemd
+    run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
   - repository: geerlingguy/docker-ubuntu1404-ansible
     version: latest
     init: /sbin/init