function getPt(n1, n2, perc) {
    var diff = n2 - n1;
    return n1 + (diff * perc);
}
Calculate a single point for a quadratic bezier curve.
Utility function used by quadraticBezierCurve.
Ignored from docs since it is not directly exposed.
@ignore
@private
@param {number} n1 - first number
@param {number} n2 - second number
@param {number} perc - percentage
@returns {number} the result