pcm2vox: fix live web audio

# Summary

Flush every write to ensure that the transcoder doesn't buffer up live audio.

Also automate building SILK and LAME with `make deps`.

# Testing

Tested on `mic-01` sending live audio to android. QA should test that and iOS also.

Once installed, `file /voxer/bin/pcm2vox` should print 64-bit.

# Deployment

The `pcm2vox` binary should come from `prod-2268:/home/djg/voxer2mp3/pcm2vox`.

[chef](https://github.com/Voxer/chef-repo/pull/138) /cc @mburns 

# Monitoring

n/a

/cc @micwehrle @georgekola @mranney