add rubocop as dev dep and configure security and frozen string cops

related to #118

Gemfile

@@ -7,16 +7,17 @@ source "https://rubygems.org/"
 gem "nokogiri", ">=1.5.9"
 gem "crass", "~>1.0.2"
 
-gem "rake", ">=0.8", :group => [:development, :test]
+gem "rake", "~>12.3", :group => [:development, :test]
 gem "minitest", "~>2.2", :group => [:development, :test]
 gem "rr", "~>1.2.0", :group => [:development, :test]
-gem "json", ">=0", :group => [:development, :test]
-gem "hoe-gemspec", ">=0", :group => [:development, :test]
-gem "hoe-debugging", ">=0", :group => [:development, :test]
-gem "hoe-bundler", ">=0", :group => [:development, :test]
-gem "hoe-git", ">=0", :group => [:development, :test]
+gem "json", "~>2.2.0", :group => [:development, :test]
+gem "hoe-gemspec", "~>1.0", :group => [:development, :test]
+gem "hoe-debugging", "~>2.0", :group => [:development, :test]
+gem "hoe-bundler", "~>1.5", :group => [:development, :test]
+gem "hoe-git", "~>1.6", :group => [:development, :test]
 gem "concourse", ">=0.26.0", :group => [:development, :test]
+gem "rubocop", ">=0.76.0", :group => [:development, :test]
 gem "rdoc", ">=4.0", "<7", :group => [:development, :test]
-gem "hoe", "~>3.17", :group => [:development, :test]
+gem "hoe", "~>3.20", :group => [:development, :test]
 
 # vim: syntax=ruby

Rakefile

@@ -28,6 +28,7 @@ Hoe.spec "loofah" do
   extra_dev_deps << ["hoe-bundler", "~> 1.5"]
   extra_dev_deps << ["hoe-git", "~> 1.6"]
   extra_dev_deps << ["concourse", ">=0.26.0"]
+  extra_dev_deps << ["rubocop", ">=0.76.0"]
 end
 
 task :gemspec do
@@ -75,6 +76,15 @@ task :generate_safelists do
   load "tasks/generate-safelists"
 end
 
+task :rubocop => [:rubocop_security, :rubocop_frozen_string_literals]
+task :rubocop_security do
+  sh "rubocop lib --only Security"
+end
+task :rubocop_frozen_string_literals do
+  sh "rubocop lib --auto-correct --only Style/FrozenStringLiteralComment"
+end
+Rake::Task[:test].prerequisites << :rubocop
+
 Concourse.new("loofah", fly_target: "ci") do |c|
   c.add_pipeline "loofah", "loofah.yml"
   c.add_pipeline "loofah-pr", "loofah-pr.yml"