[elixir-core:11317] elixirc_paths and deps including test libs separate from prod builds

Need: * I want to provide factories using ex_machina in my library projects that come into other projects as deps * I want to use ex_machina, (so please, don't recommend not using it, I've heard that many times) * I don't want ex_machina to appear as a dependency to production * I want

Re: [elixir-core:11318] elixirc_paths and deps including test libs separate from prod builds

You shouldn't need to bundle test code into your production code. 1. Deps are compiled in prod but in_umbrella deps are compiled in the same environment as the current project. You can achieve this by specifying the env option to the dependency, such as "env: Mix.env()", and it works for any