Proper lager usage

Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>

rebar.config

@@ -1,3 +1,3 @@
-{erl_opts, [debug_info, warnings_as_errors, warn_unused_vars, nowarn_shadow_vars, warn_unused_import]}.
+{erl_opts, [debug_info, {parse_transform, lager_transform}, warnings_as_errors, warn_unused_vars, nowarn_shadow_vars, warn_unused_import]}.
 {xref_checks, [undefined_function_calls, deprecated_function_calls]}.
 {eunit_opts, [verbose]}.