Add Rubocop dev support.

.rubocop.yml

@@ -0,0 +1,8 @@
+---
+inherit_from: .hound.yml
+
+AllCops:
+  Exclude:
+    - spec/dummy/**/*
+    - bin/*
+    - Guardfile

Guardfile

@@ -1,5 +1,13 @@
-guard 'rspec', cmd: 'bundle exec rspec', all_on_start: true do
-  watch('spec/spec_helper.rb')    { 'spec' }
-  watch(%r{^spec/(.+)_spec\.rb$}) { |m| "spec/#{m[1]}_spec.rb"}
-  watch(%r{^lib/(.+)\.rb$})       { |m| "spec/#{m[1]}_spec.rb" }
+group :red_green_refactor, halt_on_fail: true do
+
+  guard 'rspec', cmd: 'bundle exec rspec', all_on_start: true do
+    watch('spec/spec_helper.rb')    { 'spec' }
+    watch(%r{^spec/(.+)_spec\.rb$}) { |m| "spec/#{m[1]}_spec.rb"}
+    watch(%r{^lib/(.+)\.rb$})       { |m| "spec/#{m[1]}_spec.rb" }
+  end
+
+  guard :rubocop, all_on_start: false, cli: ['--format', 'clang', '--rails'] do
+    watch(%r{.+\.rb$})
+    watch(%r{(?:.+/)?\.(rubocop|hound)\.yml$}) { |m| File.dirname(m[0]) }
+  end
 end

spree_postal_service.gemspec

@@ -38,4 +38,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'sass-rails', '~> 4.0.0'
   s.add_development_dependency 'pry-rails', '>= 0.3.2'
   s.add_development_dependency 'guard-rspec', '>= 4.2.8'
+  s.add_development_dependency 'guard-rubocop', '>= 1.1.0'
+  s.add_development_dependency 'rubocop', '>= 0.24.1'
 end