Add a test for nested resources from a `addRestangularMethod` result

[leahciMic]

This test identifies an issue I am currently having with addRestangularMethod.

Given the following code.

var Accounts = Restangular.withConfig(function(RestangularConfigurer) {
  RestangularConfigurer.addElementTransformer('users', true, function(worker) {
    worker.addRestangularMethod('doSomething', 'get', 'do-something');
    return worker;
  });
}).service('accounts');

Accounts.doSomething().then(function(doSomething) {
  doSomething.one('foo').get();
});

I would expect doSomething.one('foo').get() to fetch accounts/do-something/foo, and not accounts/foo.

[daviesgeek]

I think this looks good, but I'll have to read over it and review it in more depth before merging. Can you squash the commits into one or two commits please?

[leahciMic]

@daviesgeek it's definitely been a while since I've used this project. I have rebased the commits for you.