It's the JavaScript way to check if something is a parent class of an object. I'm trying to stop using constructor checks, since they're all going to fail if we extend any of these classes.

	var b = Balanced.BankAccount.create();
	b.constructor == Balanced.BankAccount; // true
	b.constructor == Balanced.FundingInstrument // false
	Balanced.BankAccount.prototype.isPrototypeOf(b) // true
	Balanced.FundingInstrument.prototype.isPrototypeOf(b) // true