enforce to use Ruby 1.9 style hash syntax

.rubocop.yml

@@ -10,8 +10,8 @@ StringLiterals:
 SpaceAroundEqualsInParameterDefault:
   Enabled: false
 
-HashSyntax:
-  Enabled: false
+Style/HashSyntax:
+  Enabled: true
 
 LineLength:
   Enabled: true

Rakefile

@@ -26,7 +26,7 @@ RDoc::Task.new do |doc|
   doc.rdoc_dir = 'html'
 end
 
-task :ghpages => :rdoc do
+task ghpages: :rdoc do
   `git checkout gh-pages`
   require 'fileutils'
   FileUtils.rm_rf '/tmp/html'
@@ -35,4 +35,4 @@ task :ghpages => :rdoc do
   FileUtils.cp_r Dir.glob('/tmp/html/*'), '.'
 end
 
-task :default => :test
+task default: :test