1.0.0  Feb 27 2007
 - Initial release.
 
2.0.0  Mar 07 2007
 - Removed BCrypt::Password#exactly_equals -- use BCrypt::Password#eql? instead.
 - Added BCrypt::Password#is_password?.
 - Refactored out BCrypt::Internals into more useful BCrypt::Engine.
 - Added validation of secrets -- nil is not healthy.

2.0.1  Mar 09 2007
 - Fixed load path issues
 - Fixed crashes when hashing weird values (e.g., false, etc.)

2.0.2  Jun 06 2007
 - Fixed example code in the README [Winson]
 - Fixed Solaris compatibility [Jeremy LaTrasse, Twitter crew]

2.0.3  May 07 2008
 - Made exception classes descend from StandardError, not Exception [Dan42]
 - Changed BCrypt::Engine.hash to BCrypt::Engine.hash_secret to avoid Merb
   sorting issues. [Lee Pope]

2.0.4  Mar 09 2009
  - Added Ruby 1.9 compatibility. [Genki Takiuchi]
  - Fixed segfaults on some different types of empty strings. [Mike Pomraning]

2.0.5  Mar 11 2009
  - Fixed Ruby 1.8.5 compatibility. [Mike Pomraning]

2.1.0  Aug 12 2009
  - Improved code coverage, unit tests, and build chain. [Hongli Lai]
  - Ruby 1.9 compatibility fixes. [Hongli Lai]
  - JRuby support, using Damien Miller's jBCrypt. [Hongli Lai]
  - Ruby 1.9 GIL releasing for high-cost hashes. [Hongli Lai]

2.1.1  Aug 14 2009
  - JVM 1.4/1.5 compatibility [Hongli Lai]

2.1.2  Sep 16 2009
  - Fixed support for Solaris, OpenSolaris.

3.0.0 Aug 24, 2011
  - Bcrypt C implementation replaced with a public domain implementation.
  - License changed to MIT

3.0.1
  - create raises an exception if the cost is higher than 31. GH #27