Use --where option to specify test directory instead of just passing it as an argument in the setuptools command.
Merge pull request #604 from erosennin/master

Fix selecting specific tests in the setuptools command.  This fixes #556.
Fix a ResourceWarning in test_shared.

Thanks to Arfrever for the patch.  This fixes #593.
Fix a ResourceWarning in test_entrypoints.
Fix a ResourceWarning in test_xunit.
Get rid of another ResourceWarning in test_skips for the xunit plugin.
Fix a ResourceWarning in init_plugin.rst.