Deep merge query params onto request params

I ran the following request the other day:
```
POST /user?profession[name]="Software Writer"
profession[level]="señor"
```

Here is the `params` hash I got:
```ruby
profession: { name: "Software Writer" }
```

It seemed rather inadequate that the query parameters were not **deep** merged onto the request parameters.

This PR fixes this. The `params` hash is now:

```ruby
profession: { name: "Software Engineer", level: "señor" }
```