Chaining Expectations In MockClient

[ryber]

Is your feature request related to a problem? Please describe.
The ability to chain and order expectations in the MockClient

Describe the solution you'd like
this is a simple example. This should work but the first assert fails because the the last expect overrides the first one

      var mock = MockClient.register();
        mock.expect(GET,"http://path/one").thenReturn(FORBIDDEN);
        mock.expect(GET,"http://path/one").thenReturn(OK);

        assertEquals(FORBIDDEN, Unirest.get("http://path/one").asEmpty().getStatus());
        assertEquals(OK, Unirest.get("http://path/one").asEmpty().getStatus());