fail to work as a child project

[domenkozar]

If one has following in elm-package.json:

  "source-directories": [       
         "../src",                                                   
         "."                         
  ], 

then elm2nix generated Nix expression will only have access to current directory, failing to have access to ../src.

[domenkozar]

If we turn source directories into nix paths, this might work.

[turboMaCk]

Just so you know - I have this and #19 working in some spike sort of implementation. I'm going to open PR soon (before polishing so you can comment). Just wanted to give you heads-up - there's no need to rush.