Add RuboCop rake tasks.

Author: anolson

Rakefile

@@ -2,11 +2,14 @@
 
 require "bundler/gem_tasks"
 require "rake/testtask"
+require "rubocop/rake_task"
 
 Rake::TestTask.new do |t|
   t.libs << "lib"
   t.libs << "test"
   t.pattern = "test/**/*_test.rb"
 end
 
-task default: :test
+RuboCop::RakeTask.new
+
+task default: %i[rubocop test]