Authors:
  Justin Ethier <https://github.com/justinethier>

Contributors:
  Clint Moore <clint@ivy.io>
  Josh Triplett <josh@joshtriplett.org>
  Arseniy <https://github.com/Rotsor>
  Eli Barzilay <eli@barzilay.org>
  Ricardo Lanziano <ricardo.lanziano@gmail.com>
  Saito Atsushi <https://github.com/SaitoAtsushi>
  sw2wolf <https://github.com/sw2wolf>
  Satoshi Egi <egi@egison.org>
  Douglas Huff <https://github.com/jrmithdobbs>
  Bastian Holst <https://github.com/bholst>
  Dan Cecile <https://github.com/dcecile>
  Rohan Drape <rohan.drape@gmail.com>

References:
  Write Yourself a Scheme in 48 Hours <http://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours>
  R5RS <http://www.schemers.org/Documents/Standards/R5RS/HTML/>
  R7RS <http://trac.sacrideo.us/wg/wiki>
  CHICKEN <http://www.call-cc.org/>
  Chibi-Scheme <http://code.google.com/p/chibi-scheme/>