BugFix: to_s will preserve minus sign for negative year when formatter starts with %Y
BugFix: <=> correct for negative dates.
1.1.8 / 2012-05-30
Implemented to_s formatters.
1.1.7 / 2012-05-30
BugFix: Another logical error in to_s - fixed (formatters next).
1.1.6 / 2012-05-30
Bugfix: Checked that sign is switched off when a postive year is set after a negative year.
Bugfix: Fixed to_s again (before formatters are implemented).
1.1.5 / 2012-05-30
Allow negative years and year range from -1048576 to 1048576 (20 bits).
Implemented negative year with signing mask.
Year is no longer mandatory
Created more specific error classes
Implemented readonly attribute Date#bits to allow public access to the bit store for comparison in <=>.
Moved bits.rb back into date.rb
1.1.4 / 2012-05-29
Changed error messages for month and day to 0 - 12 and 0 - 31 respectively (since zero values are allowed).
Changed day validation logic to only check for the presence of month (not year and month - since a year has to be set before a month and is checked there).
1.1.3 / 2012-05-28
Bugfix: Fixed ZERO_DAY_MASK - which contained an extra bit, and was zeroing month when a day was set.
Check that day is set to zero if month is.
Added padding to string format for date.
1.1.2 / 2012-05-27
Fixed syntax error in example code from README.
1.1.1 / 2012-05-27
Updated tests and documentation.
1.1.0 / 2012-05-27
Implemented a 23 bit store as backing store for date,
reducing the storage requirements and increasing performance
of date objects.
1.0.0 / 2012-05-27
Refactored to use array backing store for element and computed date
values for better performance.