Upgrade rubocop to version 0.52.1 (#193)

Author: pkuczynski

CHANGELOG.md

@@ -5,6 +5,7 @@
 * Make dry-validation dependency less strict allowing to use newer versions ([#183](https://github.com/railsconfig/config/pull/183))
 * Fix `key?` and `has_key?`, which raise NoMethodError in non Rails environment, by using ActiveSupport `#delegate` implicitly ([#185](https://github.com/railsconfig/config/pull/185))
 * Update `deep_merge` dependency to latest version (v1.2.1) ([#191](https://github.com/railsconfig/config/pull/191))
+* Upgrade `rubocop` to version 0.52.1 ([#193](https://github.com/railsconfig/config/pull/193))
 
 ## 1.6.0
 

config.gemspec

@@ -41,7 +41,12 @@ Gem::Specification.new do |s|
 
   # Static code analysis
   s.add_development_dependency 'mdl',         '~> 0.4',   '>= 0.4.0'
-  s.add_development_dependency 'rubocop',     '~> 0.46',  '>= 0.46.0'
+
+  if RUBY_VERSION < '2.1'
+    s.add_development_dependency 'rubocop',     '~> 0.50',  '>= 0.50.0'
+  else
+    s.add_development_dependency 'rubocop',     '~> 0.52',  '>= 0.52.1'
+  end
 
   if ENV['TRAVIS']
     s.add_development_dependency 'simplecov', '~> 0.12.0'