function mode( a, b, c ) {
	return addon( a, b, c );
}
Returns the mode of a triangular distribution.

@private
@param {number} a - minimum support
@param {number} b - maximum support
@param {number} c - mode
@returns {number} mode

@example
var v = mode( 0.0, 10.0, 5.0 );
// returns 5.0

@example
var v = mode( 2.0, 8.0, 4.0 );
// returns 4.0

@example
var v = mode( -1.0, 5.0, 6.0 );
// returns NaN

@example
var v = mode( NaN, 10.0, 5.0 );
// returns NaN