ensure we have less than activerecord 6 for gem to function

Author: Drew-Goddyn

polymorphic_integer_type.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "activerecord"
+  spec.add_dependency "activerecord", "< 6"
   spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"