tmp commit: sncat.py may not work
sqlliteutils.py : new file with functions to help construct sqlite3
    insertion strings, and converting data to useful format.
sncat.py : Made modifications so that catalogs will be written to data,
    but have not checked if it works.
sncat.py: Modified sncat.py to write to a database sncat.db as well. The
obshistid strings are just inserted as strings to check that we can
handle things correctly. A bug was fixed because t0 was not being set in
the SNIa catalog
Added an ipython notebook to make light curve plots from the database
Added more catalogs written by writing out more instance catalogs, and at different intervals of time, so as to get a sampling of the light curve