Updated: enable method to call to not have a module path

(use __main__ by default)
Fixed: bug with sys.exit(), it shuts down also the parent's fd
Updated: Queue now use ConnAdapter because it's useful

You call enqueue() like this from the command-line:

python2 -c 'import pueuey; pueuey.Queue("my_queue").enqueue(".foo", ["bar", "baz"])'

It will use the QC_ env variable to connect to the database.