Added from_holiday, some more fixes
Delegate all date methods returning Dates to return HebrewDates
Add replace_saturday class
next() and succ() should return a new date, not modify the existing one.
Implement step(), upto() and downto()
Allow subclassing of HebrewDate with delegated methods
Fix new methods (block is undefined)
Added shabbos? and shabbat? methods
Fixed hebrew_month_to_s to return "Adar I/II"
hebrew_month_to_s slowed down way too much
Make +, -, next, back, clone faster
Better allowance for subclassing
Fix for hebrew_month_to_s crash
Fixed replacing Saturday with Shabbos in strftime