fix some code style and add checks to ci

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/eventos_web/auth_error_handler.ex

@@ -1,8 +1,11 @@
 defmodule EventosWeb.AuthErrorHandler do
+  @moduledoc """
+  In case we have an auth error
+  """
   import Plug.Conn
 
   def auth_error(conn, {type, _reason}, _opts) do
     body = Poison.encode!(%{message: to_string(type)})
     send_resp(conn, 401, body)
   end
-end
+end