Instance not properly destroyed after calling destroy()

[GatoVuelta]

Hello. I discovered my Node.js app was having a high CPU usage even after ending all streams passed to and from the mixer. Looking deeper turned out that the _read() method of the mixer class was being called nonstop (even after removing all inputs and calling mixer.destroy()).

[GatoVuelta]

The desired result (have _read() to stop and having all buffer memory freed) can be achieved only after calling mixer.close() and then mixer.destroy(), in that order, or by calling the base Readable._destroy() method. Ideally the destroy() method should be enough. And the current behaviour of destroy() should be instead called end() as it currently doesn't implement such method.

Update: CPU usage is related to #5, but was a good indicator that the stream was still going.