Accessing more user informations with the join/part events in the Hooks

Currently, Chatty seems to only handle the nickname of the user, which gives something like
`User "Foo" parted the channel "#bar`

However, more informations, such as the username, which less likely to change, cannot be exploited.

I think that Chatty should send a Struct to the hook, with available user informations when they join/part/quit.