ASGARD-1147 - Upgrade CodeNarc to 0.18.1

CodeNarc 0.18+ includes a bug fix that removes a lot of false
positives from Asgard's code violations.
https://sourceforge.net/p/codenarc/bugs/116/
Reduce CodeNarc violations
Merge pull request #305 from joesondow/ASGARD-1147-Upgrade-to-CodeNarc-0.18.1

Asgard-1147 - Upgrade to CodeNarc 0.18.1