Constrains a number within a set of bounds (range of two numbers) or returns the pointer if it is within bounds.
E.g., If pointer is less than `min` then returns `min`.  If pointer is greater than `max` returns `max`.
If pointer is within bounds returns `pointer`.
@function module:sjl.constrainPointer
@param pointer {Number}
@param min {Number}
@param max {Number}
@returns {Number}
function constrainPointer (pointer, min, max) {
        return pointer < min ? min : ((pointer > max) ? max : pointer);
    }