0.6

• FST structure modification: def_argument_tuple is no more and all arguments
  now have a coherent structure:
  • def_argument node name attribute has been renamed to target, like in assign
  • target attribute now points to a dict, not to a string
  • old name -> string are now target -> name_node
  • def_argument_tuple is now a def_argument where target points to a tuple
  • this specific tuple will only has name and comma and tuple members (no more
    def_argument for name)
• new node: long, before int and long where merged but that was causing problems