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

That part seems to be just the original from Airbnb. You're saying we're committed to semicolons, was there a conscious decision with a reasoning? Would love to know if there was. I don't really care one way or the other, but we just should strive for one style and agree on it. Ideally we can enforce that with a jshintrc configuration.

```  // Suppress warnings about unnecessary semicolons
  "-W032": true,
```
From the comment this flag might turn off all unnecessary semicolons, not just for functions. That would be too tolerant. 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.