Don't install hlink.tests as an importable module #72
Description
Right now (before and after the changes in #71), users can import hlink.tests and its submodules. This doesn't seem like a big issue to me, but it is weird. It would be nice if the tests were not a submodule of hlink. Maybe we can move them to the top-level in the directory structure so that they don't get included in the distribution and wheel? See also #67, which may go well with this issue.