Move rubocop params from .gitlab-ci.yml to Rakefile

.gitlab-ci.yml

@@ -23,7 +23,7 @@ rubocop:
   stage: check
   image: ruby:2.3.3
   script:
-    - bundle exec rubocop -D config lib spec
+    - bundle exec rake rubocop
   tags:
     - docker
   except:

Rakefile

@@ -3,3 +3,8 @@
 require 'knapsack'
 Rake.add_rakelib 'lib/gitlab/tasks'
 Knapsack.load_tasks
+
+require 'rubocop/rake_task'
+RuboCop::RakeTask.new(:rubocop) do |t|
+  t.options = ['-D', 'config', 'lib', 'spec']
+end