disallow yield in non-yield-fixtures for now. This is an incompataibility but we want to prepare for possibly merging fixture and yield_fixture some day.
strike keyword argument in favour of new pytest.yield_fixture decorator
add missing entry to CHANGELOG
fix issue358 -- introduce new pytest_load_initial_conftests hook and make capturing initialization use it, relying on a new (somewhat internal) parser.parse_known_args() method.