Allow single file applications to be run with Ace

[CrowdHailer]

To try this escript now it can be installed as follows.

mix escript.install github crowdhailer/ace branch escript

You can either add the escript dir to you path or just call it directly.

./.mix/escript/ace server.exs

Example server.exs file

use Raxx.SimpleServer

def handle_request(_request, _config) do
  response(:ok)
  |> set_body("Hello, world!")
end