Parse sentences into years, months, and days field

Don't autocommit, though this doesn't help database performance
much.

Move database config to local settings.
Add fields and logic to store IUCR offenses based on statutes
Update South version requirements.

South 1.0 doesn't seem to support Python 3.
Add dev requirements for IPython notebook
Add final_statute field and have only one set of IUCR fields

Add a final_statute field to reflect either the ammended statute
if it's present, or the statute if its not.  Base the IUCR code
field on the final statute.  Remove separate IUCR fields for
the ammended statute.
Put analysis IPython notebook under revision control
Add count of records, cases.
s/Conviction/Disposition/

Update model names and calling code to reflect the realization that
records in our data are dispositions, not convictions.

This initially seemed like extra work, but we'll need an actual
Conviction model which we'll extract from the Disposition models.
This will make the queries a lot easier and faster.

Addresses https://github.com/sc3/cook-convictions/issues/41
Update the IPython notebook
Add Conviction model

Add a Conviction model to hold distinct convictions, interpretted
from the disposition records.

Add a management command to create Conviction models from Dispositions.

Add some database indices and QuerySet helper methods to make getting
the earliest dispositions in a case faster.

Addresses https://github.com/sc3/cook-convictions/issues/41
Update IPython notebook

Update our IPython notebook.
Merge pull request #1 from ghing/master

Models and management commands to create Convictions from Dispositions