Avoid error with redcarpet not installed

Author: benoittgt

Gemfile

@@ -21,12 +21,8 @@ else
 end
 
 gem 'yard', '~> 0.9.24', :require => false
-
-### deps for rdoc.info
-group :documentation do
-  gem 'redcarpet', :platform => :mri
-  gem 'github-markup', :platform => :mri
-end
+gem 'redcarpet', :platform => :mri
+gem 'github-markup', :platform => :mri
 
 if RUBY_VERSION < '2.0.0' || RUBY_ENGINE == 'java'
   gem 'json', '< 2.0.0'