Data files get installed incorrectly

[jaraco]

When installing the package under tox (with usedevelop=False), the data files get installed in the wrong location. For example, I've created such a tox environment and here's what you find for tutorial.conf:

$ find .tox/dist-check -name tutorial.conf 
.tox/dist-check/cherrypy/tutorial/tutorial.conf

I would have expected the file to get installed at .tox/dist-check/lib/python3.6/site-packages/cherrypy/tutorial/tutorial.conf. I suspect there's some interaction between tox and pip and the hacks created in #586. Possibly also implicated is #1090.