fixes 5512 - fixing content view delete performance issues
Fixes #5518 - Repository.enabled no longer exists
Fixes #5534 - Set version on angular-rails-templates gem

Fixing uninitialized constant AngularRailsTemplates::Engine::Tilt
Fixes #5542 - Remove rubocop cop SymbolName
Fixes #5544 - Add alternate nvm setup for Node.js
refs #4919 - fixing improper apidoc for `system-group list`
Fixes #5548 - Add gemnasium to tell us about outdated gem requirements

Gemnasium will tell us if our gems are outdated. Most importantly, it also
notifies us if there are security patches. Also, I'm removing the old Travis
badge.
Fixes #5186, #5189 - Content Host - show provisioning details and cross-link to Foreman host

This commit contains a few basic changes, including:

1. Add a foreign key to katello's system to enable associating it to a foreman host
2. Add a 'Provisioning Details' tab to a katello content host
3. Add high-level information from foreman to the provisioning details.  At this time,
   this includes the information that is currently shown from foreman host list,
   such as name, status, OS, puppet environment, last puppet report, model & host group.
4. Provide cross-linking (where possible) from the katello content host to the foreman host.
   This currently supports linking to the host as well as hostgroup.
Fixes #5008 Manifest History not updated on import

- importing/deleting/reloading manifest file also triggers update/display of manifest
  history
- BZ1077893
- exposes import history in subscriptions v2 api