Updated README
Created geohash.py

geohash.py contains the actual xkcd algorithm. It takes date and
the DJIA opening value as parameters and is thus 30W Rule agnostic.
It is up to the invoking function to handle 30W logic prior to
invoking geohash.geohash.
Added get_todays_djia function to utils.callouts

This function wraps get_external_djia. It attempts to get today's
DJIA opening price from carabiner.peeron.com and, if it fails,
it will check again in two minutes. If today's DJIA opening price is
already found in the database then the function simply returns.

The function is meant to be invoked by a daily cron job running around
9:30am EST.