Support specifying Adjustment state for fetch requests

I've made a few small changes to support specifying Adjustment state for fetch requests. 

I also increased the visibility of doGET because with this visibility I would have been able to append the state parameter to a fetch URL without modifying the client code at all. 
The code:

```
.append((type != null ? "?type=" + type.getType() : "")).append((state != null ? "&state=" + state.getState() : ""))
```

is actually incorrect. If `type` is null, but not `state`, the url will be `&state=pending` instead of `?state=pending`.

> 23:35:13,610 WARN  ~ Recurly error whilst calling:
> https://api.recurly.com:443/v2/accounts/32/adjustments?type=charge%3Fstate%3Dpending&&per_page=20

Looking at your request, it is decoded as `?type=charge?state=pending` instead of `?type=charge&state=pending`. I can't see where that could be set from the patch you sent. Are you using the same code? Could you check-in the test your are running?

> That's why in a previous email I inquired whether you could think of
any build time tasks in Maven that perhaps would result in the source being
encoded for some reason

I didn't see that email but there is no encoding done at build time.