Remove some FLAKY tests from appveyor that should no longer be FLAKY; add test_selectors for 3.5/3.5 because it has timeout-related code that can be flaky there. Remove obsolete failure from PYPY case because we don't support that old version anymore.

test_hub_join_timeout was still flakey on Py 3.4/64-bit appveyor

One finer-grained skip for appveyor