add skippy stdout callback

It removes the teal lines when a host is skipped for a task. This makes the output less spammy and much easier to read. Empty TASK blocks are still included in the output, but that's ok.

ansible.cfg

@@ -7,3 +7,4 @@ host_key_checking=False
 gathering = smart
 fact_caching = jsonfile
 fact_caching_connection = /tmp
+stdout_callback = skippy