use string instead of ints for urls and values in tests
use string instead of ints for urls and values in tests

strings are more widely correct as ints will be represented correctly,
and it will allow using the `__str__` of any custom type used in the
model id field

tabo/django-treebeard,django-treebeard/django-treebeard,tabo/django-treebeard,tabo/django-treebeard,django-treebeard/django-treebeard,django-treebeard/django-treebeard,tabo/django-treebeard