Add a piezo element for audio in Rev A HW

[57Bravo]

I was able to use a piezo element to get my beepberry to speak using espeak. It would be nice if the next rev of HW had a buzzer/piezo for indications and audio.

A little tinny, but it's usable.

beeper_speaks.mp4

[sockbot]

Could you upload a schematic and a BOM to this request so that I could look into reproducing it? Pictures of hardware install would be great too.

[57Bravo]

Sure thing. I pushed the repo here.

https://github.com/57Bravo/BeepSensors

I'll add some notes on the SW tonight. It's basically just using raspi-gpio to map GPIO to a pwm audio device. You can use anything that works with alsa. Play, ffmpeg, etc.