Add alembic revision for category constraint in project
Add category constraint to app/project model field
Update theme
Fix model tests
Fixed blog tests
Use FactoryBoy in blogpost tests
Fix scheduler tests
Merge pull request #907 from PyBossa/issue-868-category-constraint

Issue 868 category constraint
Merge branch 'master' into issue-repositories

* master:
  Fix scheduler tests
  Use FactoryBoy in blogpost tests
  Fixed blog tests
  Fix model tests
  Update theme
  Add category constraint to app/project model field
  Add alembic revision for category constraint in project

Conflicts:
	test/test_view/test_blog.py