tox: use deps for pluggymaster testenvs
tox: use deps for pluggymaster testenvs

https://github.com/tox-dev/tox/issues/706 has been fixed.

nicoddemus/pytest,pytest-dev/pytest,The-Compiler/pytest,Akasurde/pytest,markshao/pytest,tomviner/pytest,alfredodeza/pytest,The-Compiler/pytest,tomviner/pytest,RonnyPfannschmidt/pytest,nicoddemus/pytest