Fix elixir_logger/2 (#510)

* Fix elixir_logger/2

* Improve test coverage

Author: thiagogsr

lib/new_relic/logger.ex

@@ -82,7 +82,7 @@ defmodule NewRelic.Logger do
 
   defp elixir_logger(:debug, message), do: Logger.debug(message)
   defp elixir_logger(:info, message), do: Logger.info(message)
-  defp elixir_logger(:warn, message), do: Logger.warning(message)
+  defp elixir_logger(:warning, message), do: Logger.warning(message)
   defp elixir_logger(:error, message), do: Logger.error(message)
 
   @sep " - "

test/logger_test.exs

@@ -36,6 +36,8 @@ defmodule LoggerTest do
     previous_logger = GenServer.call(NewRelic.Logger, {:logger, :logger})
     NewRelic.log(:info, "HELLO")
     NewRelic.log(:error, "DANG")
+    NewRelic.log(:warning, "OOPS")
+    NewRelic.log(:debug, "SHHH")
     GenServer.call(NewRelic.Logger, {:replace, previous_logger})
   end
 end