Add function to remove attempted offense statute

Add a function to remove the statutes for attempted offenses
from statute citation strings.  This should make it easier to
parse statutes for looking up IUCR codes.

Add a management command to export a CSV of all statutes that
seem to have the attempted offense statutes in them to help
prepare test cases.
Better statute parsing

Improve statute parsing to assign IUCR codes, descriptions and
category more Disposition and Conviction records.

Strip out the part fo the statute that
identifies the crime as attempted, conspiracy or solicitation.

Improve the regexes used for parsing statues and
make a cleaner API for parsing the statute that tries to do
less in each function.

Make a lookup table to correct badly formed statutes in cases
where trying to fix the regex is too difficult or impossible.

Make use of the functionality that Brian
added to python-iucr that tries to look up the statute with
varying numbers of subsection bits.
Merge branch 'master' into better_iucr_code_detection
Update loading of final statute and IUCR fields

Add final_statute_formatted field to the Disposition and Conviction
model.

Add a format_statute() function to format the parsed statute that will
go into final_statute_formatted.

Factor final_statute field population out into a method,
load_final_statute.

Remove trailing whitespace from files edited in this commit.

Rename statute2iucr management command to load_final_statute_and_iucr to
reflect these changes.

Fix statute.strip_surrounding_parens to handle empty string

Addresses https://github.com/sc3/cook-convictions-data/issues/7,
https://github.com/sc3/cook-convictions/issues/83
Add statute-based queries

Add statute-based queries to group together violent, nonviolent,
affecting women and drug crimes (and index crimes within each)
to handle cases where an ILCS statute doesn't map to an IUCR code
or the mapping is ambiguous.

Addresses https://github.com/sc3/cook-convictions/issues/83,
https://github.com/sc3/cook-convictions-data/issues/7,
https://github.com/sc3/cook-convictions-data/issues/6