ISO 8601 date methods

Prototype methods:

• parse(str): creates instance date using iso format string
• toIsoString(): converts instance date to iso format string
• toString(): core date prototype toString method (inheritance issues)
• getWeek(): returns instance date week number
• isToday(): returns true if instance date is today
• isTomorrow(): returns true if instance date is tomorrow
• sameDate(date): returns true if instance date is the same day (y,m,d)
• sameTime(date): returns true if instance date is the same day (hour, min, ms)

Static methods:

• parse(str): creates new iso date instance using iso format string
• toIsoString(date): converts date to iso format string (2008-07-09T16:13:30+12:00)
• toLocalIsoString(date): converts date to local iso format string (2008-07-09T16:13:30Z)