Fix error when running tests

Was seeing
`calling logger:remove_handler(default) failed: :error {:badmatch, {:error, {:not_found, :default}}}`
when running tests. According to a GitHub issue[1], the fix is to start
`lager` before `logger`.

[1]: erlang-lager/lager#507 (comment)

mix.exs

@@ -14,7 +14,7 @@ defmodule Lightrail.MixProject do
 
   def application do
     [
-      extra_applications: [:logger]
+      extra_applications: [:lager, :logger]
     ]
   end