Add support for configuring Nagios Event Brokers
Fix default hash setting to meet upstream standards
Add host escalations

* http://nagios.sourceforge.net/docs/3_0/objectdefinitions.html#hostescalation
Merge pull request #243 from scottso/fix_empty_pagerduty_key

Fix using wrong pagerduty key attribute
Merge pull request #239 from kewubenduben/master

Add host escalations
Merge pull request #235 from aashley/master

Add support for configuring Nagios Event Brokers
Merge pull request #242 from scottso/allow_missing_user_databags

Allow an empty set of users for the user databag.
Add the ability to ignore items

This lets us ignore certain roles, environments and/or operating systems
when the cookbook is generating hosts/hostgroups to monitor.  This
allows us to have some items maintained by chef but not mointored by
nagios.

Change-Id: I6de02228b9514bcc8e1e1f18c15ed3a91a79bd0b