Batch of Updates

Neat idea!  Here is the clean-up it took to get it working for me.

This addresses a few issues I found:

* new (still undocumented) Google STT v2 API support
* differentiate errors from "not understood"
* some typos
* simplified random file selection (probably still could collapse those into a single one)
* fixed sound player on MacOS (didn't work for me, running Mavericks)
* added some text to the README to help with dependencies
* relaxed error handling so KeyboardInterrupt and SystemExit still work