Fix build dependency on deprecated msgpack unpacker api call.

As this project has been idle for awhile it looks like a deprecated
method on msgpack::unpacker was causing the build to break for the
latest and greatest msgpack-c library. More specifically the method
msgpack::unpacker::rewind_buffer no longer exists. In reading the
current msgpack-c code it looks like the correct fix here is to
simply remove the call to rewind_buffer (refer to unpack.h).
Fixed a missed call to setup the server dispatcher.

In the server base class the listen wrapper that takes an ip address
and port did not correctly setup the dispatcher for the server which
was resulting in asserts in the boost library when accessing the
servers disaptcher via a shared pointer at a downstream point of
execution.