Cleanup: Use centralized method for aptly detection

Fixes bug with empty node[apt]
Merge pull request #467 from fh/t/fix-nil

Cleanup: Use centralized method for aptly detection
Enhancement: spec for nginx-app::redirector
Enhancement: support for granular URL-based redirects

Related: getcourse/issues#559
Fix: rubocop
Enhancement: implement this using a map {}
Merge branch 't/redirector-fun' of github.com:till/easybib-cookbooks into t/redirector-fun