[Rakefile] Remove references to Ruby 1.9

We don't support Ruby 1.9 anymore.

Rakefile

@@ -166,7 +166,7 @@ begin
       Rake::Task['examples:build'].invoke
 
       title 'Running RuboCop'
-      Rake::Task['rubocop'].invoke if RUBY_VERSION >= '1.9.3'
+      Rake::Task['rubocop'].invoke
     end
 
     desc "Rebuild all the fixture tarballs"
@@ -279,13 +279,11 @@ begin
 
   #-- Rubocop ----------------------------------------------------------------#
 
-  if RUBY_VERSION >= '1.9.3'
   require 'rubocop/rake_task'
 
   RuboCop::RakeTask.new(:rubocop) do |task|
     task.patterns = ['lib', 'spec']
   end
-  end
 
 rescue LoadError, NameError => e
   $stderr.puts "\033[0;31m" \