Add Rubocop support to Rakefile

Rakefile

@@ -1,6 +1,7 @@
 require 'rubygems'
 require 'bundler/setup'
 require 'rspec/core/rake_task'
+require 'rubocop/rake_task'
 
 # Immediately sync all stdout so that tools like buildbot can
 # immediately load in the output.
@@ -8,7 +9,7 @@ $stdout.sync = true
 $stderr.sync = true
 
 # Change to the directory of this file.
-Dir.chdir(File.expand_path("../", __FILE__))
+Dir.chdir(File.expand_path('../', __FILE__))
 
 # This installs the tasks that help with gem creation and
 # publishing.
@@ -16,7 +17,13 @@ Bundler::GemHelper.install_tasks
 
 # Install the `spec` task so that we can run tests.
 RSpec::Core::RakeTask.new(:spec) do |t|
-  t.rspec_opts = "--order defined"
+  t.rspec_opts = '--order defined'
 end
+
+desc 'Run RuboCop'
+RuboCop::RakeTask.new(:rubocop) do |task|
+  task.options << '--display-cop-names'
+end
+
 # Default task is to run the unit tests
-task :default => :spec
+task default: :spec