play_ringbuffer doesn't loop

[tomstoll]

Hello. We have a project where we're trying to use rtmixer to play sounds that continuously loop. We thought the RingBuffer class and play_ringbuffer would allow us to do that, but it doesn't seem to loop. I noticed "looping?" is listed under planned functionality in the docs, so we wanted to check if we totally misunderstood the intended functionality before we continued debugging.

For reference, we've been discussing the issue here.