Add default env vars to the .app.src file

src/lager.app.src

@@ -4,8 +4,7 @@
  [
   {description, "Erlang logging framework"},
   {vsn, "1.0.0"},
-  {modules, [
-            ]},
+  {modules, []},
   {applications, [
                   kernel,
                   stdlib
@@ -13,5 +12,13 @@
   {registered, []},
   {mod, {lager_app, []}},
   {env, [
+            %% What handlers to install with what arguments
+            {handlers, [{lager_console_backend, info},
+                {lager_file_backend, [{"log/error.log", error},
+                {"log/console.log", info}]}]},
+            %% Whether to write a crash log, and where. Undefined means no crash logger.
+            {crash_log, "logs/crash.log"},
+            %% Whether to redirect error_logger messages into lager
+            {error_logger_redirect, true}
         ]}
  ]}.