Add a health monitoring page

[bess]

Use this gem: https://github.com/lbeder/health-monitor-rails

• [ ] the endpoint should be /health
• [ ] change the honeybadger monitoring to look at /health and check for the absence of ERROR
• [ ] configure it to report errors to honeybadger Check for:
  • [ ] database
  • [ ] solr
  • [ ] cache