Add order invoice property to submitTransaction and authorizeTransaction

[kylecannon]

This doesn't break backwards compatibility with anything due to adding in the property via extending the Order Model.

Example:

    var Order = require('42-cent-model').Order;
    var OrderProperties = {
        invoiceNumber: 'AAAAAA-1234555'
    };

    var Order = new Order(OrderProperties);

[lorenzofox3]

it seems to break the build

[kylecannon]

I couldn't get the tests to pass at all even without my changes present. Do you want to run the tests without my changes and see if the tests pass on your end?