Issue 3994 email visible on assignment page for non-mod user

This commit contains the fix and the tests: only show email link if the user can see assignments.

Tests test that the mod can still see the email link, while the non-mod user can't.
Issue 3994

This is all just spacing and indentation :D
3336 I spelled Kristin's name wrong. Also the humanized model names meant the test no longer worked
Merge pull request #1746 from sarken/issue_3336

3336 Test update
Merge pull request #1743 from CristinaRO/issue-3994-email-visible

Issue 3994 email visible on assignment page to a non-mod user
3750 Always use the tag name in works page headings
3750 Change warning display to Creator Chose Not To Use Archive Warnings
issue 4041 Make bookmark processing less realtime
Merge pull request #1748 from sarken/issue_3750

3750 Change Author to Creator and use tag name in headings
3750 Expire cache on work modules
Merge pull request #1750 from sarken/issue_3750

3750 Expire cache on work modules
Merge pull request #1749 from zz9pzza/issue_4041

issue 4041 Make bookmark processing less realtime