edited typo in sandbox.rst
Tougher tests for category browsing

Verify that a correct URL leads to no redirect, and verify that an
incorrect URL leads to a redirect and the redirect has the correct URL.
New URL scheme for permanent category URLs

The old one was too identical to the product URL scheme and caused
issue #765. There really isn't a good way to keep them in the same
"namespace", hence all category browsing will happen under
/catalogue/category now.