Safely publishing packages

[artemeff]

Is locked by hexpm/hex#656

[dealloc]

this seems to be implemented upstream!
I just tested this with

  defp hex do
    [
      api_url: "http://localhost:4000/api",
      api_key: "SECRET"
    ]
  end

and it seems to work :)

[artemeff]

@dealloc yea, I know, this issue stands for readme updating :))