release 0.0.20

Author: seuros

declarative.gemspec

@@ -17,6 +17,7 @@ Gem::Specification.new do |spec|
   end
   spec.test_files    = spec.files.grep(%r{^(test)/})
   spec.require_paths = ["lib"]
+  spec.required_ruby_version = '>= 2.3.0'
 
   spec.add_development_dependency "rake"
   spec.add_development_dependency "minitest"