[packaging] ship tests with sdist, not with bdist #75
Description
It's common practice to ship project's tests with sdist because it can contain files that are useful for development or build process (e.g. downstream packaging). But tests are useless for runtime and should not be included into bdist (wheel).
In case of setuptools build backend including/exclusion can be configured:
https://setuptools.pypa.io/en/latest/userguide/miscellaneous.html#controlling-files-in-the-distribution