Add utils module, cleanup `ipc://` files on close

Use `utils.log_label` along with `logging.getLogger` to label log messages
using the module path to the currently running function.

For example:

    import logging
    from utils import log_label

    class Foo:
        def bar(self):
            logging.getLogger(log_label(self)).info('log relative to an object')

    def my_func():
        logging.getLogger(log_label()).info('log from within a function')
Clean-up repo, rename modules, etc.
Add Python setup.py file for distutils
Modify ZeroMQ stream callback signature

Modify ZeroMQ stream callback signature to pass `env` dictionary as
first argument.  The `env` dictionary currently includes the following
keys/items:

    `socks`: Ordered dictionary of label/socket pairs
    `streams`: Ordered dictionary of label/stream pairs
    `io_loop`: Parent IO-loop object
    `ctx`: Parent ZeroMQ context