update rebar.lock

This was missed when pbkdf2 was added and esockd was updated.
mochiweb silently got an update, which I wouldn't have realised
if not for this.

rebar.lock

@@ -1,6 +1,6 @@
 [{<<"esockd">>,
   {git,"https://github.com/emqtt/esockd",
-       {ref,"6ef597f16ce242fe37ae019d6ff5214f7a784c80"}},
+       {ref,"87d0d3b672e0f25e474f5f8298da568cbb6b168a"}},
   0},
  {<<"gen_logger">>,
   {git,"https://github.com/emqtt/gen_logger.git",
@@ -24,7 +24,11 @@
   0},
  {<<"mochiweb">>,
   {git,"https://github.com/emqtt/mochiweb",
-       {ref,"af27c0c90bf4c1bfeae0290e4c541264b69f7168"}},
+       {ref,"c75d88e451b4fe26580a58223f645d99482f51af"}},
+  0},
+ {<<"pbkdf2">>,
+  {git,"https://github.com/comtihon/erlang-pbkdf2.git",
+       {ref,"7076584f5377e98600a7e2cb81980b2992fb2f71"}},
   0},
  {<<"syslog">>,
   {git,"git://github.com/Vagabond/erlang-syslog",