Add Composer support (Small change)

I've left this change intentionally small it should in now way affect current usages of WhatsAPI.

Before merging make sure to edit the **authors** part of the composer.json.

Only autloading of the `WhatsProt` and all classes in the events dir is done. From what I could find these are the only classes consumers communicate with?

This fixes #602
Maybe you still want to change this?