Gemfile in serviceworker-rails-0.3.1 vs Gemfile in serviceworker-rails-0.4.0

@@ -1,12 +1,15 @@
-source 'https://rubygems.org'
+source "https://rubygems.org"
 
 # Specify your gem's dependencies in serviceworker-rails.gemspec
 gemspec
 
 group :development, :test do
+  gem "rubocop", "0.39.0"
+
   unless ENV["TRAVIS"]
-    gem "pry-byebug", platforms: [:ruby_23]
+    gem "pry"
+    gem "pry-byebug", platforms: [:mri]
     gem "guard"
     gem "guard-minitest"
   end
 end