Added mags_using_photometry: illustrates the use of catsim photutils
methods to calculate magnitudes and compares them to SNCosmo magnitudes.
Added timing function
snObject.py is a class describing supernova properties in terms of
attributes. It does not know how to communicate with the catalog, but
inherits from ``sncosmo.Model`` of a particular form. It has methods to
calculate mags using the photUtils framework
Note that the SNObject class is throwing some nan values that I still
don't understand
Added sncat.py as the new instance catalog file