Simplified OP 0 (Dispatch) handling
Simplified OP 0 (Dispatch) handling

- Instead of having a separate function for every dispatch type (which all did the same thing anyway), we now just have on_dispatch which looks at the Type ('t') and calls the matching callback function (if defined). Ultimately it is not this library's job to do anything with the information it receives from the gateway except pass it on to the caller.
- A few other simplifications to dispatch handling also means that all dispatch types are supported now as callback functions.

vsTerminus/Mojo-Discord,vsTerminus/Net-Discord