TagsController limited to owner only

The owners should be the only ones allowed to make mass changes to the
tags. Set TagsController to only work with the owner role. Added 'tags'
to the dropdown menu for owners.
Tag modification batch size limited to 100

To help stop cursor timeouts, we are limiting the tag modification batch
size to only 100 contacts per call.
Fixed #81: Cancel new contact no longer causes 500 error

When you cancel new contact -- a person or a company -- the controller
will take you to the respective people index or companies index. The
rendered content used partials dependent on the contacts directory. This
fixed the dependency by explicitly linking to contacts/.
Fixed #82: Placeholder text no longer saved as tags

The best_in_place placeholder text for tags is "Click to add tags
(lowercase letters, numbers & hyphens only)". Some browsers entered the
placeholder text into the field. It was highlighted so it was easily
erased. However, if the user hit ENTER, it would save the text as the
tags. This change catches the tag grouping and filters it out.