Add rubocop task to travis

Author: rodjek

.travis.yml

@@ -6,10 +6,18 @@ branches:
   only:
     - master
 bundler_args: --without development system_tests
+script:
+    - bundle exec rake $CHECK
+env:
+    - CHECK=test
 rvm:
   - 1.9.3
   - 2.0.0
   - 2.1.10
   - 2.2.7
   - 2.3.4
   - 2.4.1
+matrix:
+    include:
+        - rvm: 2.4.1
+          env: CHECK=rubocop

Rakefile

@@ -17,4 +17,14 @@ rescue LoadError
   $stderr.puts 'Changelog generation requires Ruby 2.0 or higher'
 end
 
+begin
+  require 'rubocop/rake_task'
+
+  RuboCop::RakeTask.new(:rubocop) do |task|
+    task.options = %w[-D -E]
+  end
+rescue LoadError
+  $stderr.puts 'Rubocop is not available for this version of Ruby.'
+end
+
 # vim: syntax=ruby