*
@method is[Day]()
@returns Boolean
@short Returns true if the date falls on that day.
@extra Also available: %isYesterday%, %isToday%, %isTomorrow%, %isWeekday%, and %isWeekend%.

@set
isToday
isYesterday
isTomorrow
isWeekday
isWeekend
isSunday
isMonday
isTuesday
isWednesday
isThursday
isFriday
isSaturday

@example

Date.create('tomorrow').isToday() -> false
Date.create('thursday').isTomorrow() -> ?
Date.create('yesterday').isWednesday() -> ?
Date.create('today').isWeekend() -> ?

**
@method isFuture()
@returns Boolean
@short Returns true if the date is in the future.
@example

Date.create('next week').isFuture() -> true
Date.create('last week').isFuture() -> false

**
@method isPast()
@returns Boolean
@short Returns true if the date is in the past.
@example

Date.create('last week').isPast() -> true
Date.create('next week').isPast() -> false

*
function buildRelativeAliases() {
    var special  = 'today,yesterday,tomorrow,weekday,weekend,future,past'.split(',');
    var weekdays = English['weekdays'].slice(0,7);
    var months   = English['months'].slice(0,12);
    extendSimilar(date, true, false, special.concat(weekdays).concat(months), function(methods, name) {
      methods['is'+ simpleCapitalize(name)] = function(utc) {
       return this.is(name, 0, utc);
      };
    });
  }