function mean( mu ) {
	return addon( mu );
}
Returns the expected value of a degenerate distribution.

@private
@param {number} mu - constant value of the distribution
@returns {number} expected value

* @example
var v = mean( 0.1 );
// returns 0.1

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

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

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