Added Centos 6 as target platform

.travis.yml

@@ -1,5 +1,10 @@
 sudo: required
 env:
+  - distribution: centos
+    version: 6
+    init: /sbin/init
+    run_opts: ""
+    container_id: $(mktemp)
   - distribution: centos
     version: 7
     init: /usr/lib/systemd/systemd

tests/Dockerfile.centos-6

@@ -0,0 +1,11 @@
+FROM centos:6
+RUN yum -y update; yum clean all;
+RUN yum -y install epel-release
+RUN yum -y install git ansible sudo
+RUN yum clean all
+# Disable requiretty
+RUN sed -i -e 's/^\(Defaults\s*requiretty\)/#--- \1/'  /etc/sudoers
+# Install Ansible inventory file
+RUN echo -e '[local]\nlocalhost ansible_connection=local' > /etc/ansible/hosts
+CMD ["/usr/sbin/init"]
+