http://reefpoints.dockyard.com/2013/11/05/design-patterns-command-pattern.html
http://reefpoints.dockyard.com/2013/10/01/design-patterns-composite-pattern.html
http://brainspec.com/blog/2012/11/07/delegation-with-forwardable/
http://www.sitepoint.com/value-objects-explained-with-ruby/
http://blog.bigbinary.com/2013/07/07/visitor-pattern-and-double-dispatch.html
http://www.intridea.com/blog/2012/2/21/imbue-a-module-configuration-pattern-for-ruby http://blog.rubybestpractices.com/posts/gregory/059-issue-25-creational-design-patterns.html http://sourcemaking.com/refactoring/feature-envy
http://sourcemaking.com/design_patterns
https://github.com/Integralist/Ruby-Design-Patterns
https://github.com/shvets/design_patterns_in_ruby
https://practicingruby.com/articles/responsibility-centric-vs-data-centric-design?u=dc2ab0f9bb
https://practicingruby.com/articles/adventure-in-prototypes?u=dc2ab0f9bb
http://www.sitepoint.com/ways-activesupport-helps-ruby-developers/
http://www.sitepoint.com/guide-ruby-collections-iii-enumerable-enumerator/
- AST - Abstract syntax tree