Version 6.0, January 2014
 Removed unstable/file
 unstable/error: added raise-syntax-error*
 unstable/syntax: added syntax-length

Version 5.3.6, August 2013
 unstable/match: added match*?

Version 5.3.4, May 2013
 Added unstable/redex
 Added unstable/socket
 Added unstable/macro-testing
 Added unstable/options
 Renamed option/c (from unstable/contract) to maybe/c

