Gemfile in image_optim_rails-0.4.1 vs Gemfile in image_optim_rails-0.4.2

@@ -1,16 +1,11 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 gemspec
 
-%w[
-  rails
-  sprockets
-  sprockets-rails
-].each do |gem_name|
-  version = ENV[gem_name.tr('-', '_').upcase + '_VERSION']
-  gem gem_name, version if version
-end
+gem 'appraisal'
 
 if RUBY_VERSION >= '2.0'
   gem 'travis_check_rubies', '~> 0.2'
 end