Removing hidden edit link. Fixes ndlib/planning#303.

NOTE: #link_to_edit_permissions is no longer being used.
However, all the tests are for #link_to_edit_permissions not #permission_badge_for.
It would have been _better_ to refactor the tests as well. Sorry.
Merge pull request #267 from ndlib/remove-hidden-edit-link

Removing hidden edit link. Fixes ndlib/planning#303.