Add skip_pull_runtimes for Travis CI (#30)

diff --git a/ansible/environments/local/group_vars/all b/ansible/environments/local/group_vars/all
index bccaacf..1b3fe54 100755
--- a/ansible/environments/local/group_vars/all
+++ b/ansible/environments/local/group_vars/all
@@ -29,9 +29,8 @@
 
 env_hosts_dir: "{{ playbook_dir }}/environments/local"
 
+skip_pull_runtimes: true
 runtimes_manifest:
-  defaultImagePrefix: "openwhisk"
-  defaultImageTag: "latest"
   runtimes:
     nodejs:
     - kind: "nodejs:6"