Constructor for ZarinPal object.
@param {String} MerchantID
@param {bool} sandbox
function ZarinPal(MerchantID, sandbox) {
	if (typeof MerchantID === 'string' && MerchantID.length === config.merchantIDLength) {
		this.merchant = MerchantID;
	} else {
		console.error('The MerchantID must be ' + config.merchantIDLength + ' Characters.');
		return false;
	}
	this.sandbox = sandbox || false;

	this.url = (sandbox === true) ? config.sandbox : config.https;
}