suppress alsa warnings

[neuromusic]

see http://stackoverflow.com/questions/7088672/pyaudio-working-but-spits-out-error-messages-each-time

[siriuslee]

I'll take a go at this.

[siriuslee]

So, after working a bit on this, the solution suggested by Nils Werner in the stackoverflow thread works nicely. There are a few remaining warnings that are not produced by alsa that should perhaps also be suppressed, namely:

Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started

Also, instead of completely suppressing these warnings, I propose we convert them to logging debug messages whenever we get around to implementing that.

[siriuslee]

This blog post is relevant: http://blog.yjl.im/2012/11/pyaudio-portaudio-and-alsa-messages.html