ci: Changes to CI configuration and support ruby 2.5 and 2.6

ci: Changes to CI configuration and support ruby 2.5 and 2.6

Author: Mikemosca

.rubocop.yml

@@ -79,7 +79,7 @@ AllCops:
   # is specified in the Gemfile or gems.rb file, RuboCop reads the final value
   # from the lock file.) If the Ruby version is still unresolved, RuboCop will
   # use the oldest officially supported Ruby version (currently Ruby 2.2).
-  TargetRubyVersion: 2.5
+  TargetRubyVersion: 2.3
   # What version of Rails is the inspected code using?  If a value is specified
   # for TargetRailsVersion then it is used.  Acceptable values are specificed
   # as a float (i.e. 5.1); the patch version of Rails should not be included.