Create proper installation script

[pganssle]

Right now the installation script is a mess - you need to manually create your virtualenv, then pip install this thing, then do a whole bunch of other configuration. For the first pass at an install script, I want a reasonable workflow that will:

1. Create a virtual environment for you in the right place.
2. Install audio-feeder for you.
3. Be idempotent - i.e. it should serve to upgrade your current version if it doesn't exist.