Move hack from test_views.py to factories.py

The python 2 JSON encoder has a known issue with UTF-8 characters, and this
limitation is compensated for by creating sub-par random data. Move this hack
from test_views.py to factories.py. If we ever upgrade to python 3, we can now
remove the hack from a single place in the source code, instead of multiple
locations.
Fix errors in urls.py

Documentation for the /category/* URLs is wrong. Fix it. The
/category/create-form/ URL pattern is missing entirely. Add it.
Add tests for /category/* views.
Implement views for /category/* URLs.

Also add empty HTML templates. These templates are completely empty. However,
they must exist for the views to function correctly.