Enhancement: add install for lua and python

[jakobpederson]

[private]

[mattjmorrison]

@jakobpederson I don't think this is what you wanted to do... I think you wanted to change

brew install vim --with-lua

to

brew install vim --with-lua --with-python3

[emrygun]

Or brew install vim --with-lua --without-python --with-python3 as an alternative. Produces almost the same effect.