* tests: refactor and cleanup
* refactor: more consistent
* tests: vendor six
* tests: more xfails, nicer system
* tests: simplify to info
* tests: suggestions from @YannickJadoul and @bstaletic
* tests: restore some pypy tests that now pass
* tests: rename info to env
* tests: strict False/True
* tests: drop explicit strict=True again
* tests: reduce minimum PyTest to 3.1
The new version of pytest now reports Python warnings by default. This
commit filters out some third-party extension warnings which are not
useful for pybind11 tests.
* Add `pytest.ini` config file and set default options there instead of
in `CMakeLists.txt` (command line arguments).
* Change all output capture from `capfd` (filedescriptors) to `capsys`
(Python's `sys.stdout` and `sys.stderr`). This avoids capturing
low-level C errors, e.g. from the debug build of Python.
* Set pytest minimum version to 3.0 to make it easier to use new
features. Removed conditional use of `excinfo.match()`.
* Clean up some leftover function-level `@pytest.requires_numpy`.
