- main topic
 d+ Object is parent of all class 
 d+ Implement skeleton of Rubyish::Hash, Rubyish::Array, Rubyish::String
  + overload print function. If parameters is object in Rubyish, call #to_s automatically
  + C extesion, "" return String object, [] {} return Array and Hash object respectively.
 d+ TrueClass, and true syntax
  + FalseClass, and false syntax
  + rewrite Object#ancestors to show all ancestors
  + rewrite Kernel#puts to identify whether object is Rubyish or not

- Object
 d+ #__id__
 d+ #inspect 
  + rewrite #methods, no longer return special word

- Class
  + #public
  + #private
  + #protected

- Kernel
 d+ #Hash()   #=> return Rubyish::Hash  
 d+ #Array()  #=> return Rubyish::Array 
 d+ #String() #=> return Rubyish::String

- Module

- Hash

- Array

- String

