nereid.cms.article.category Model has no attribute 'uri' #2129

* This patch has replaced 'uri' with 'unique_name' as there is no self
  attribute 'uri' in nereid.cms.article model.

Task ID: project-7/task-2129
Issue ID: 299003
Merge pull request #16 from simmianand/feature/task-2129

nereid.cms.article.category Model has no attribute 'uri' #2129