When stop the application, deregister raven error logger.

When stop the application, displayed error report.

(egg@127.0.0.1)1> q().
ok
(egg@127.0.0.1)2> 
=ERROR REPORT==== 10-Mar-2014::18:57:54 ===
** gen_event handler raven_error_logger crashed.
** Was installed in error_logger
** Last event was: {error_report,<0.66.0>,
                      {<0.69.0>,supervisor_report,
                        [{supervisor,{local,gr_counter_sup}},
                        {errorContext,child_terminated},
                        {reason,killed},
                        {offender,
                            [{pid,<0.90.0>},
                              {name,gr_lager_default_tracer_counters},
                              {mfargs,
                                  {gr_counter,start_link,
                                      [gr_lager_default_tracer_counters]}},
                              {restart_type,transient},
                              {shutdown,brutal_kill},
                              {child_type,worker}]}]}}
** When handler state == []
** Reason == {noproc,
                {gen_server,call,
                    [httpc_manager,
                      {request,
                          {request,undefined,<0.6.0>,0,https,
                              {"sentry.example.com",443},
                              "/api/store/",[],post,
                              {http_request_h,undefined,"keep-alive",
                                  undefined,undefined,undefined,undefined,
                                  undefined,undefined,undefined,undefined,
                                  undefined,undefined,undefined,undefined,
                                  undefined,undefined,"sentry.example.com",
                                  undefined,undefined,undefined,undefined,
                                  undefined,undefined,undefined,undefined,
                                  undefined,[],
                                  ["raven-erlang/","fd8dff7"],
                                  undefined,undefined,undefined,"0",undefined,
                                  undefined,undefined,undefined,undefined,
                                  undefined,
                                  [{"x-sentry-auth",
                                    ["Sentry sentry_version=2.0,sentry_client=raven-erlang/",
                                    "fd8dff7",",sentry_timestamp=",
                                    "1394445474456628",",sentry_key=",
                                    "SENTRY_KEY"]}]},
                              {"application/octet-stream",
                              <<"DUMMY_DATA">>},
                              {http_options,"HTTP/1.1",infinity,true,
                                  {essl,[]},
                                  undefined,false,infinity,false},
                              "https://sentry.example.com/api/store/",[],none, 
                              [],1394445474473,undefined,undefined,false}},
                      infinity]}}