Add traffic modules for performance platform dashboard
Merge pull request #770 from alphagov/feature/publish--pp-dashboard

Add traffic modules for performance platform dashboard
Remove computed date diffs from tests

Having a hard-coded date and a computed diff means that that test will fail and need fixing once a year.

By stubbing the method we stop being dependent on the date diffs actually matching the current date.
Merge pull request #772 from alphagov/bugfix/dates-lol

Remove computed date diffs from tests