Allow for option to turn message into JSON

[wa1ker38552]

Allows users to represent their Message object as json instead. This could be helpful when working with client side scripts since you don't need to manually create a new dictionary and extract values from the object before sending. You could just directly send the Message.json dictionary instead.

[dolfies]

This is a waste of memory; providing dictionary representations of Discord models is not in the scope of this library.

[dolfies]

@wa1ker38552 While I don't really recommend this, you can use underlying HTTP methods in client.http to get raw models if you really need to.