Added directory on position distribution  of snIa starting out
with trying to understand the variables in the galaxy catalog.
Still having trouble with snIa.py and the code will crash. I had tried
to use an instance of sncosmo.Model as an attribute of the instance class.
sncosmo.Model is itself inherited off an abstract class and uses a setter
based on that. Somehow in this situation, I am unable to set values. I have
to work out why this is happening.