Make Selector fully private

[carllerche]

Currently, Selector is only public in order to support the Evented trait which exposes the type as part of it's API. It should be possible to fix this.

[reem]

Just to make sure - do you plan to have outside types able to implement Evented? I've implemented Evented for a few types in other crates, but I could also work around it if it became impossible. (though I'd rather not :P)

[carllerche]

It should be plausible to make it private and let you implement Evented as long as you can proxy the call to some other Evented type that you own.

[reem]

The implementation (all methods) can be private, but the type itself has to be exposed if it's part of the method signatures on Evented.

[nixpulvis]

Related see #319.

[carllerche]

The strategy here will be to have Evented take an EventLoop reference vs. a Selector reference. Internal to Mio implementations of Evented will be able to access the selector via EventLoop, implementations external to Mio can proxy to other Evented types.

[carllerche]

Fixed on master