0.2.0 (May 12, 2017)
  Allow nested environment changes in the same thread

0.1.0 (January 7, 2017)
  Remove ActiveSupport dependency

0.0.4 (January 6, 2017)
  Improved thread safety
  Handle TypeErrors during assignment
  Improve documentation

0.0.1 (November 28, 2012)
  Initial release