[TASK] Add balance_change array to transaction response, computed from metadata

> That part seems to be just the original from Airbnb

Yep

> was there a conscious decision with a reasoning

The ripple-lib I inherited didn't have style that was ideal to me personally, but I kept most of the existing features. I find it readable; there's no reason to change.

> but we just should strive for one style and agree on it

We've already been adhering to the style, more or less, until now.

> From the comment this flag might turn off all unnecessary semicolons, not just for functions.

JSHint isn't very good for style enforcement like this (you can't enforce indentation levels either). It's nothing to go crazy about.

> If there's a way to allow just function semicolons with a reasoning we can express to other teams, them I'm all for it.

(a) We've been doing it this way from the beginning
(b) There's no reason to change
(c) We don't have to do what every other team does. The client team still uses [variable-assigned constructors](https://github.com/ripple/ripple-client/blob/develop/src/js/tabs/trade.js#L9), which I think our jshintrc might catch. This is fine. It's a stylistic choice for the most part. There is nothing to enforce here.