Represent-boundaries

* Eliminate Django 1.7 deprecation warning.

* Set default value on `jsonfield` fields.

* Use `jsonfield` instead of `django-jsonfield`.

* Support shapefiles with binary field names.
* Recurse directories and ZIP files in `loadshapefiles`.
* `loadshapefiles` will not create a boundary set if no shapefiles are found.

Identified quirks:

* If a shapefile has `_cleaned_` in its name, it will not be loaded, unless created by Represent Boundaries.

* Fix regression with `loadshapefiles` skip logic.

* Remove the `--database` (`-u`) option from the `loadshapefiles` management command, which would only specify the database in which to find the `spatial_ref_sys` table.
* Make non-integer `offset` error message consistent with non-integer `limit` error message.
* `format=wkt` and `format=kml` no longer error in Django 1.7.
* I18n support.
* Add tests.

Identified quirks:

* The `shape`, `simple_shape` and `centroid` endpoints ignore the `pretty` parameter.