add rubocop-daemon support

see https://github.com/fohte/rubocop-daemon

Author: kaptron

Gemfile

@@ -180,6 +180,7 @@ group :development do
   gem 'guard', require: false
   gem 'guard-rspec', require: false
   gem 'rubocop', require: false
+  gem 'rubocop-daemon', require: false
   gem 'spring'
   gem 'spring-commands-rspec'
   gem 'spring-watcher-listen', '~> 2.0.0'

Gemfile.lock

@@ -489,6 +489,8 @@ GEM
       rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 1.7)
+    rubocop-daemon (0.3.2)
+      rubocop
     ruby-next-core (0.9.2)
     ruby-progressbar (1.10.1)
     ruby_dep (1.5.0)
@@ -669,6 +671,7 @@ DEPENDENCIES
   rolify (~> 5.2.0)
   rspec-rails (~> 3.9)
   rubocop
+  rubocop-daemon
   sass-rails (~> 5.0)
   schmooze
   scout_apm