Removed unused import from xri.py
Use plain query dict instead of Message instance in TestCompleteMissingSig
Use Consumer.complete instead of _get_response in TestCompleteMissingSig
Use correct return_to instead of patching its verification in TestCompleteMissingSig
Get rid of explicit GenericConsumer instance in TestCompleteMissingSig
Remove unused CatchLogs from TestCompleteMissingSig
Use standard assertEqual for successful test in TestCompleteMissingSig
Use Consumer.complete instead of Consumer._get_response in TestSetupNeeded
Use Consumer.complete instead of Consumer._get_response in test_completeGoodReturnTo
Simpler query setup in test_completeGoodReturnTo
Check response.status instead of response's class.
Make ConsumerTest not depend on Consumer._get_response.

- Mock Consumer.complete instead.
- Since Consumer.complete does session cleanup as a side effect,
  it can no longer be tested in ConsumerTest. Cleanup tests are
  separated into their own case: Cleanup.
- Temporarily mark test_successDifferentURL as skipped, it should
  eventually go into Cleanup as well.
Remove StubConsumer used ConsumerTest.

By now StubConsumer was only used in test_begin which effectively
was testing our own mock _beginWithoutDiscovery which doesn't make
sense.
Inline Consumer._get_response
Remove makeKVPost from GenericConsumer
Move _checkSetupNeeded to Consumer.
Rewrite _checkSetupNeeded to return a value instead of raising an exception. Also rename to setup_url
Move setup_url to Message.
Moved _doIdRes to Consumer.
Inline Consumer._doIdRes

- Tests use Consumer.complete for now but many of them should
  check individual features instead of calling the most
  general function and patching out everything they're not
  interested in.
- Creation of a successful complete query extracted into
  _success_query. Should be used more from now on.