Make ViewObservables consistent with each other

As discussed in https://github.com/ReactiveX/RxAndroid/pull/20. Resolves https://github.com/ReactiveX/RxAndroid/issues/7 as well.
just a general style remark. The test name isn't very good at documenting the desired behavior. It could as well be called "testThatItWorks" and would convey the same information :-) I prefer tests that are small and focused, with ideally only given-when-then case. This helps tremendously when trying to understand what the exact behavior under different cases is (happy path, sad path, corner cases)