luigid as a console entry point through setup.py

Having a separate cli.py module and a console entrypoint in setup.py is a bit more convenient if luigi is installed using package managers (pip easy_install or just setup.py), since it will get installed into the python environment.  otherwise, the bin directory is not part of the egg and hence the wrapper around luigi.server.run() gets lost.

Not sure how much utility this might have for most luigi users.