TODO list for Sidef

Classes:
    * Implement roles (from Perl 6) and add the `does` trait for classes
      (http://doc.perl6.org/language/objects#Roles)

Blocks:
    * Find a better way to implement the `next` and `break` statements (optionally, accept next(n) and break(n))

Method/functions:
    * Implement the `is export` trait for functions and classes (maybe)

Speculations:
    * Make all core methods (including user-defined methods) real multimethods, using Class::Multimethods.
    * Replace the current numerical system with Math::BigNum.
    * Bootstrap Sidef by writing a code generator in Sidef that generates Perl code.
    * Rewrite all core libraries in Sidef.
