Don't make kernel or rabbit params necessary (as they're not)

Neither of these is necessary. A further refactor is probably required to allow one to just pass in one mega hash like:

``` ruby
{
  kernel: { ... },
  rabbit: { ... },
  mnesia: { ... }
}
```

And so forth. But that's further down the line. For now, this allow you to edit one config while not deleting the other if, say, the values change.