Minor updates
Minor updates

- Remove all mention of "version 0" versus "version 1" source trees, in
  attempt to make @pfmoore more comfortable :-)
- Add note that we still aren't actually sure whether a prefix alone is
  enough to specify an editable install target, to make sure this
  doesn't get lost.
- Fix typo "negotation" (thanks @xavfernandez)
- Remove stray leftover references to ``pypackage.cfg`` (thanks @rmcgibbo)

pypa/interoperability-peps