Arecord silent crash fix

It turns out arecord stops streaming audio data after 2GB of recorded data, causing Sonus to stop listening after ~18 hours. To mitigate this, Sonus now creates a new arecord sub-process after 1.5GB of data is streamed.

The only downside to this mitigation, is that it's not a totally seamless transition from one stream to another. If you're mid-utterance when the change happens, the remainder of the utterance will not be streamed to the cloud detector. Still better than crashing 🖖

For a detailed description of the issue, see: #94