Napari integration test

As a plugin developer, I would like an integration test that verifies that the plugin can be built, and then loaded by the current Napari release.

Andy Sweet has offered to help us with this, and has offered this example (not what i have in mind, but perhaps a starting point for a unit test):

https://github.com/andy-sweet/napari-metadata/pull/65/files#diff-1ac48cb1f11d2dc2970e9da2889e0faa08cbe37a9e88b3a6674966dcfa1219ce