add code_change to oc_reporter to make otp-19 happy (#117)

Author: tsloughter

src/oc_reporter.erl

@@ -27,6 +27,7 @@
          handle_call/3,
          handle_cast/2,
          handle_info/2,
+         code_change/3,
          terminate/2]).
 
 -include("opencensus.hrl").
@@ -95,6 +96,9 @@ handle_info(report_spans, State=#state{reporter=Reporter,
     send_spans(Reporter, Config),
     {noreply, State#state{timer_ref=Ref1}}.
 
+code_change(_, State, _) ->
+    {ok, State}.
+
 terminate(_, #state{timer_ref=Ref}) ->
     erlang:cancel_timer(Ref),
     ok.