add emqtt app

rel/reltool.config

@@ -47,6 +47,7 @@
        {app, lager, [{mod_cond, app}, {incl_cond, include}]},
        {app, esockd, [{mod_cond, app}, {incl_cond, include}]},
        {app, mochiweb, [{mod_cond, app}, {incl_cond, include}]},
+       {app, emqtt, [{mod_cond, app}, {incl_cond, include}]}
        {app, emqttd, [{mod_cond, app}, {incl_cond, include}]}
       ]}.