Download and load census tables from the IRE census site

Create a shell script that's a version of
https://github.com/ireapps/census/blob/master/tools/sql/ire_export/load_psql.sh
modified to use sqlite

Add a fabric task that runs this script
SQLAlchemy wrapper for census data tables

Also restructure to be a bit more package-like.
Use spatialite if available, strip header line
Load tract shapes into database

Add a fabric task and ORM mappings for loading and querying
Chicago Census Tract shapes from
https://data.cityofchicago.org/Facilities-Geographic-Boundaries/Boundaries-Census-Tracts-2010/biqm-wjk3

What I really want this for is to filter the values from the P12
census tables down to just tracts in Chicago (since the CSV data
loaded for the P12 table is for all of Illinois).

http://stackoverflow.com/a/15962062/386210 and
http://lucumr.pocoo.org/2011/7/19/sqlachemy-and-you/ were extremely
helpful in figuring out how to do this.