SelectorEventLoop is never released

[v-lavrentikov]

In the SelectorEventLoop initializer you call setReader() method with a callback handler. This callback handler retains self object reference. Thus deinit() method will never be called after releasing SelectorEventLoop reference.
To release object it is needed to call removeReader() method first. It is public, but it parameter pipeReceiver is a private field. It looks like something went wrong.

[fangpenlin]

Hey @v-lavrentikov, thanks for reporting! That's a good caught. Yep, indeed it's creating a reference cycle there, I've already created a PR here #60, will soon merge it and make a new release once the tests pass.