rubocop corrections

Gemfile

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
@@ -32,12 +34,14 @@ gem 'jquery-rails'
 # Reduces boot times through caching; required in config/boot.rb
 gem 'bootsnap', '>= 1.4.4', require: false
 
+gem 'rubocop', require: false
+
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
-  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
-  gem 'rspec'
-  gem 'rspec-rails', ">= 2.0.0.beta"
+  gem 'byebug', platforms: %i[mri mingw x64_mingw]
   gem 'rails-controller-testing'
+  gem 'rspec'
+  gem 'rspec-rails', '>= 2.0.0.beta'
 end
 
 group :development do
@@ -45,8 +49,8 @@ group :development do
   gem 'web-console', '>= 4.1.0'
   # Display performance information such as SQL time and flame graphs for each request in your browser.
   # Can be configured to work on production as well see: https://github.com/MiniProfiler/rack-mini-profiler/blob/master/README.md
-  gem 'rack-mini-profiler', '~> 2.0'
   gem 'listen', '~> 3.3'
+  gem 'rack-mini-profiler', '~> 2.0'
   # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
   gem 'spring'
 end
@@ -60,4 +64,4 @@ group :test do
 end
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
-gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
+gem 'tzinfo-data', platforms: %i[mingw mswin x64_mingw jruby]