IMG-519 Require non-empty category on description save, remove blank option when category is chosen, pre-filter blank option when db already has a non-nil id
IMG-528 Additions to Book model
IMG-539 Record timestamp for deleted users and books
We can set up a page where we can see the deleted users and deleted books.
IMG-528 Additions to Book model
IMG-539 Record timestamp for deleted users and books
We can set up a page where we can see the deleted users and deleted books.
Revert "IMG-528 Additions to Book model"

This reverts commit 279e96e61d75ce8e23bfa02d53526bcc4114e10b.
IMG-519 Sync left and right panels, dynamic update of guidelines
IMG-519 categories with no guidelines should clear the guideline div
Merge remote-tracking branch 'heroku/master'
IMG-539 Record timestamp for deleted users and books
IMG-431 Removed div-to-iframe conversion
Merge branch 'deleted_at_refactoring' of heroku.com:diagram-staging
IMG-419 Not all the images at Diagram Help page are clickable.
IMG-543 Corrected audit population, switched to direct SQL statements for speed.
Merge remote-tracking branch 'heroku/master'