This commit refactors IrcClientFuture and ConnectionFuture to own
the config instead of holding a reference.
This is required for reconnecting in dynamic contexts.
This is not possible with the old API, because Config is a reference,
requiring the value to live for the whole execution of the reactor.
Changed all involved structs to take `Config`s, rather than borrow them - this is due to `'static` requirement that is bound to crop up somewhere, when spawning a future into a reactor/runtime.
Updated examples and docs to reflect the change.
