Tox-envfile

What's Changed
* Apply updates from cookiecutter by seanh in https://github.com/hypothesis/tox-envfile/pull/7
* Add manual testing instructions by seanh in https://github.com/hypothesis/tox-envfile/pull/8
* Apply updates from cookiecutter and add support for Python 3.7 by seanh in https://github.com/hypothesis/tox-envfile/pull/9


**Full Changelog**: https://github.com/hypothesis/tox-envfile/compare/0.0.4...0.0.5

What's Changed

* Updates from cookiecutter by seanh in https://github.com/hypothesis/tox-envfile/pull/1, https://github.com/hypothesis/tox-envfile/pull/4 and https://github.com/hypothesis/tox-envfile/pull/5
* Fix crash when no `-e` by seanh in https://github.com/hypothesis/tox-envfile/pull/6

**Full Changelog**: https://github.com/hypothesis/tox-envfile/compare/0.0.3...0.0.4

Apply cookiecutter template