Now supporting custom (de)serialization

It now makes difference between unicode and bytes types, by using a prefix;
the only drawback is we have to subclass the "fallback" Python-only
version -> test that for performance, or find a better way to do this!

(Maybe, add support for a callback around "raw" (de)serialization?)
Add script to time serialization functions
Merge branch 'custom-msgpack-serialization'
Added support for custom serialization methods
Added benchmarks for custom serialization methods
Now allowing Server/Client to use custom serialization methods