When using releases, Pipeline still uses Mix.env()

[fibrasek]

So we ran into a problem when using releases (mix release/mix phx.gen.release) with the PhoenixGon.Pipeline plug, on it's source it's using Mix.env() and for some reason that is not being resolved when you create a release.

I have no solution for it yet, but I thought of creating an issue for those who run into the same problem as us.

[khusnetdinov]

@fibrasek PR welcome!

[fibrasek]

@khusnetdinov I don't remember how we solved this, but next week I can take some time to create a PR based on that solution :)

[khusnetdinov]

Thanks!