added setup.py (renamed sos to sos.py. sos command is avail. after install)

Hallo Jeroen,

I added a very basic `setup.py` to your projects, which makes available `sos` from the command line and also lets you do things like `from sos import x2d`. The `iris.csv` example file is copied to the same directory that sos is installed to (in my case that is `/usr/local/lib/python2.7/dist-packages/sos-0.1.0-py2.7.egg/sos/`).

Before adding this to PyPI, the readme probably should be converted to the .rst format.

Groetjes,
Arne