Remove all altitudes from WKT (not just 0s) for must_be_two_d
Fix a typo in a comment in fix_invalid_geos_multipolygon
Increase maximum length of Code.code to 500 characters

Most of the codes used for police forces by the police API are
longer than 10 characters, the previous limit. As mentioned in
commit 19e1b312424e8cec211f183973a140f835fddff2, PostgreSQL only
uses the minimum storage space needed for varchar fields in any
case.
Add a generic invalid-geometry-fixing function
Add a --fix_invalid_polygons option to mapit_import
Add options to mapit_import to allow overriding of name and code

Names and codes for areas are not always present as fields within
data files and they may need to be imported from other sources,
for example filenames or data fetched via APIs. The options
added in this commit allow a name and a code to be specified
to use for areas to be imported from a file. A warning is shown
if multiple areas are found in the file, which would create
areas with duplicate names and/or codes.
Add a script to import police force area boundaries

Police force boundaries for England, Wales and Northern Ireland
are now published as KML files under the UK Open Government
Licence at:

  http://data.gov.uk/dataset/police-force-boundaries-england-and-wales

This dataset does not include names or codes for the areas
within the KML files. The filenames correspond to the force
IDs used by the police API, so they are stored as codes and
the force names are fetched and saved via the API at:

  http://data.police.uk/api/forces

This script calls the generic mapit_import script to handle
the KML files and save the areas. It accepts and passes on
all of that command's behaviour-related options.
Fix allowing no code to be set, as noticed by Matthew Somerville
Fix typo
Add a couple of tests for the area views.
Add travis config.
Use local render function rather than generic view.
Evade caching, unknown test running order.