rollup by contacts' failures

- rollup logic implemented after notification rule logic in Notification#messages
- basic feature tests added
- rollup threshold is added to the contact model, api and web gateways
- gems updated to latest (bundle update) including tzinfo, active_support, rspec, etc
- s/mock/double/ in all specs to fix rspec deprecation warning
- maintenance on a check removes it from alerting lists
- email and sms alert texts moved to erb templates
- email and sms templates for rollup (problem and recovery) added

I'm updating the wiki docs as I go