/*This class converts dates to and from ISO 8601 strings. A good introduction to ISO 8601: <http://www.cl.cam.ac.uk/~mgk25/iso-time.html>
*Parsing can be done strictly, or not. When you parse loosely, leading whitespace is ignored, as is anything after the date.
*The loose parser will return an NSDate for this string: @" \t\r\n\f\t 2006-03-02!!!"
*Leading non-whitespace will not be ignored; the string will be rejected, and nil returned. See the README that came with this addition.
*The strict parser will only accept a string if the date is the entire string. The above string would be rejected immediately, solely on these grounds.
*Also, the loose parser provides some extensions that the strict parser doesn't.
*For example, the standard says for "-DDD" (an ordinal date in the implied year) that the logical representation (meaning, hierarchically) would be "--DDD", but because that extra hyphen is "superfluous", it was omitted.
*The loose parser will accept the extra hyphen; the strict parser will not.
*A full list of these extensions is in the README file.
/*The format to either expect or produce.
*Calendar format is YYYY-MM-DD.
*Ordinal format is YYYY-DDD, where DDD ranges from 1 to 366; for example, 2009-32 is 2009-02-01.
*Week format is YYYY-Www-D, where ww ranges from 1 to 53 (the 'W' is literal) and D ranges from 1 to 7; for example, 2009-W05-07.
//The default separator for time values. Currently, this is ':'.