Added Method#arity emthod

TagAction: tag 'fails' deleted for specs:

 * Method#arity returns n, where n is the number of required arguments,
   when there are zero or more required arguments only
 * Method#arity returns n, where n is the number of required arguments
   and method created via defined_method
 * Method#arity returns -(n+1), where n is the number of required
   arguments, when there is at least one optional argument
 * Method#arity returns -(n+1), where n is the number of required
   arguments, when there is a splat argument,
   regardless of optional arguments
 * Method#arity returns the same value regardless of the presence of a block
Make RPython happy
remove unused import
Implemented Kernel#respond_to_missing? (almost)

Not implemented only case with private method

 * Kernel#respond_to_missing? is called with a 2nd argument of
   false when #respond_to? is
 * Kernel#respond_to_missing? is called a 2nd argument of false
   when #respond_to? is called with
 * Kernel#respond_to_missing? is called with true as the second
   argument when #respond_to? is
 * Kernel#respond_to_missing? is called when #respond_to? would return false
 * Kernel#respond_to_missing? causes #respond_to? to return true
   if called and not returning fal
 * Kernel#respond_to_missing? causes #respond_to? to return false if called
   and returning false
 * Kernel#respond_to_missing? causes #respond_to? to return false if called
   and returning nil
 * Kernel#respond_to_missing? is called for missing class methods
 * Kernel#respond_to_missing? returns true if obj responds to the given
   public method
Simplified code a little bit
Refactored code to use polymorphism

This commit also removes hack with bytecode and block attributes
Merge pull request #541 from krekoten/kernel_respond_to_missing

Implemented Kernel#respond_to_missing? (almost)
Merge pull request #539 from krekoten/method_arity

Method arity almost completed
Hash#{to_s,inspect} based on Array#inspect
Merge pull request #542 from jstepien/hash-to-s

Hash#{to_s,inspect} based on Array#inspect
Numeric#{floor,round,ceil}
Use Coerce.float instead of sending to_f
Merge pull request #543 from jstepien/numeric-floor-round-ceil

Numeric#{floor,round,ceil}
nested module and class naming
renamed domainerror