Returns the string representation of a number, with placeholders added.
@param {Number} n The number to add the placeholders to.
@param {String=} [placeholder=','] Typically the comma (,). The string that seperates the thousanths place.
@return {String} The number formatted with placeholders.
function (n, placeholder) {
                    if(n === undefined || n === null || !libs.object.isNumeric(n)) return n;
                    placeholder = typeof placeholder === 'string' ? placeholder : '.';
                    var rest, idx, int, ns = n.toString(), neg = n < 0;

                    idx  = ns.indexOf('.');
                    int  = parseInt(Math.abs(n), 10).toString();

                    if(idx > -1) rest = '.' + ns.substring(idx + 1, ns.length);
                    return (neg ? '-' : '') + libs.string.reverse(libs.string.reverse(int).replace(/(\d{3})(?!$)/g, '$1,')) + (rest || '');
                }