Made alicorn into a real program.

I've added a real script (`scripts/alicorn`) to launch alicorn with, replacing
`python -m alicorn.run` with something a little more installation-friendly.
I've also added the requisite `distribute` glue to allow alicorn to be
installed by `pip` or `easy_install`, or manually.
Add setuptools/distribute glue and launcher script for alicorn.