Compare NSDate with comparison operators

NSDate+Comparable.swift

public func <(a: NSDate, b: NSDate) -> Bool {
    return a.compare(b) == NSComparisonResult.OrderedAscending
}


public func >(a: NSDate, b: NSDate) -> Bool {
    return a.compare(b) == NSComparisonResult.OrderedDescending
}


public func ==(a: NSDate, b: NSDate) -> Bool {
    return a.compare(b) == NSComparisonResult.OrderedSame
}


public func >=(a: NSDate, b: NSDate) -> Bool {
    return a > b || a == b
}


public func <=(a: NSDate, b: NSDate) -> Bool {
    return a < b || a == b
}


extension NSDate: Comparable {}