Fix ranges test infrastructure

[Michael Schellenberger Costa (miscco)]

We get errors due to ambiguous symbols of test::iterator and std::iterator (thanks using namespace std;)
Explicitely pull in test::iterator and test::range for good measure too

[Stephan T. Lavavej (StephanTLavavej)]

I have traditionally preferred to name test machinery differently than Standard machinery to avoid any potential for ambiguity (as I've been a huge fan of using namespace std; in tests); MeowIterator and to a slightly lesser extent meow_iterator are clearly non-Standard. That said, I certainly defer to Casey Carter (@CaseyCarter) on ranges test conventions.

[Casey Carter (CaseyCarter)]

Thanks for the cleanup, Michael Schellenberger Costa (@miscco)!