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. 
> I completely understand the hesitation. However do consider that there are
many API parameters that the client doesn't currently support.

Yes, but I'm hoping the library will be feature complete eventually.

> I'm still unable to get my
modified getAccountAdjustments() method working.

What's the issue? Do you have a stack trace?