The ValidatorContext.prototype.validateMultipleOf function is not working properly for negative numbers

[simonmrog]

The calculation of the remainder in the validateMultipleOf function (line 776 in the tv4.js file) is wrong for the case in which the data is a negative number, in which case the modulus changes sign and the function returns null instead of returning the corresponding error.

The reason is that the [CLOSE_ENOUGH_LOW, CLOSE_ENOUGH_HIGH] interval validation fails since CLOSE_ENOUGH_LOW >= 0 and for negative numbers remainder <= 0.
One fix to this issue may be to use the absolute value in the remainder to consider both signs:

ValidatorContext.prototype.validateMultipleOf = function validateMultipleOf(data, schema) {
	var multipleOf = schema.multipleOf || schema.divisibleBy;
	if (multipleOf === undefined) {
		return null;
	}
	if (typeof data === "number") {
		var remainder = Math.abs((data / multipleOf) % 1);
		if (remainder >= CLOSE_ENOUGH_LOW && remainder < CLOSE_ENOUGH_HIGH) {
			return this.createError(ErrorCodes.NUMBER_MULTIPLE_OF, {value: data, multipleOf: multipleOf}, '', '', null, data, schema);
		}
	}
	return null;
};

With this implementation (proposed in PR #282) the function returns the same error for a number both positive and negative with the same schema.