Handle virtualenvs with pyenv

[humitos]

• https://github.com/ssbb/pyenv-mode-auto
• https://smythp.com/emacs/python/2016/04/27/pyenv-elpy.html
• https://github.com/gregnewman/emacs.d/blob/master/greg.org#python--elpy
• https://github.com/jorgenschaefer/elpy/issues/803

[humitos]

Enough with just setting the env variable: https://github.com/humitos/emacs-configuration/commit/b6f0edb

[humitos]

Maybe this package is what I want,

https://github.com/proofit404/pyenv-mode