Upgrade sensu and module

Successfully provisioned a monitoring-1 and backup-box-1 with this,
after provisioning with master

Settings required for latest puppet module

 - Be explicit about the api
 - Need to specify a version of the sensu plugin gem
 - The puppet module changed the default vhost to not include a slash -
   https://github.com/sensu/sensu-puppet/pull/184

This unfortunately broke our setup, which expected a slash in the vhost.
Add uchiwa puppet module and config

Uchiwa replaces the sensu dashboard

Uchiwa defaults to using port 3000, so set the nginx alerts upstream to use that