support cluster/replicated mode

[dixudx]

• support two modes: standalone (default mode) and replicated mode;
• update template configuration files and playbooks to enable cluster mode;
• fully test on Ubuntu and Redhat against these two modes;

[JasonGiedymin]

I'm not opposed to this PR in intent. Two things I'd like to see:

• verify 'cluster' mode install works via vagrant, with two nodes specified in the vagrant file
• bump the playbook version to v0.9.1.

@ninthnails, anything you'd to add?

[JasonGiedymin]

@dixudx don't give up on this :-) If we can get a vagrant test validating cluster mode that would be great.

[JasonGiedymin]

@ninthnails I support this if you think it worthy. Would added documentation help?

[ernestas-poskus]

@dixudx closing in favor of https://github.com/AnsibleShipyard/ansible-zookeeper/releases/tag/v0.9.2

role now supports hash and lists hosts