Refactoring / minor fixes / update CoffeeScript

  * A new `default_config` object with default values and
    callback-implementations.
  * Move `failed` flag from `Lexer` and `Parser` to `CoffeeScriptParser`
  * Demote `get_class_name` to a simple function (instead of method).
  * Move rewritten `pair` to `lexer.coffee`.
  * Fix: Interpolations are now lexed with the correct Lexer-class.
  * Catch "Parsing halted" error from Jison to avoid needlessly logging
    to stderr (for a failed error recovery).
  * Very slight improvements in comments.
  * CoffeeScript 3650d6e (post 1.6.2)
Show docco headings in the structure tree.

  * Process single-line comments, collect headings and add them to
    the structure tree (with respect to their level).
  * Add option, help and test.
Fix logic error in `name_from_value`.