Bump rails to 5.2 and update rubocop

Gemfile

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 git_source(:github) do |repo_name|
@@ -6,7 +8,7 @@ git_source(:github) do |repo_name|
 end
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
-gem 'rails', '~> 5.1.7'
+gem 'rails', '~> 5.2.4.3'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
@@ -24,11 +26,11 @@ gem 'jbuilder', '~> 2.5'
 gem 'activeadmin'
 gem 'devise'
 
+gem 'auto_strip_attributes'
 gem 'bootstrap'
 gem 'jquery-rails'
 gem 'rack-canonical-host'
 gem 'recaptcha', require: 'recaptcha/rails'
-gem 'auto_strip_attributes'
 gem 'scenic'
 
 group :development, :test do