Util.inspect Depth not deep enough

I was testing the response bodies of my API and came across the problem that the more deeply nested objects were not being parsed.

I would get the following,

```
{
id: 1,
title: 'Tech Lead',
createdAt: '2019-05-19T07:56:54.307Z',
updatedAt: '2019-05-19T07:56:54.307Z',
Attempts: [
{
id: 1,
status: 'Pending',
createdAt: '2019-05-19T07:56:54.307Z',
updatedAt: '2019-05-19T07:56:54.307Z',
UserId: 1,
InterviewId: 1,
User: [Object]
}
]
}
```

Note the `User: [Object]` which should be my full User object.

I've made changes to `util.inspect` so that all deeply nested objects will now show properly.
E.g, `util.inspect(body, { depth: null });`

See [PR](https://github.com/visionmedia/supertest/pull/577)