Revert "`mix deps.get` does not use MIX_ENV"
Revert "`mix deps.get` does not use MIX_ENV"

This reverts commit 1e9cd551ce6fe2406e4b664a67faa8660d722201.

ggcampinho/elixir,kelvinst/elixir,antipax/elixir,kelvinst/elixir,gfvcastro/elixir,antipax/elixir,joshprice/elixir,pedrosnk/elixir,beedub/elixir,kimshrier/elixir,ggcampinho/elixir,beedub/elixir,gfvcastro/elixir,lexmag/elixir,elixir-lang/elixir,kimshrier/elixir,lexmag/elixir,pedrosnk/elixir,michalmuskala/elixir