Add error checking to the python bindings. They previously didn't check
for a NULL response from the libstatgrab functions - which resulted in
python core dumping. It now raises an exception instead.
Also add a first stab at a setup.py so people can quickly build/install
this extension if they want.

Add libstatgrab python wrapper. This won't be installed with libstatgrab,
or in fact have anything done to it - it's just there if people want it.
If it matures, I'll consider making it a package in it's own right.