function mode( mu ) {
	return mu;
}
Returns the mode of a degenerate distribution.

@param {number} mu - constant value of distribution
@returns {number} mode

@example
var v = mode( 0.1 );
// returns 0.1

@example
var v = mode( 0.5 );
// returns 0.5

@example
var v = mode( 10.0 );
// returns 10.0

@example
var v = mode( NaN );
// returns NaN