This change aims to polish up the existing checklist UI as well as its code base.
On the UI:

Shifted the UI to be fixed at the bottom (better than in the middle of nowhere)
Uses existing Reviewboard icons as buttons (versus textual buttons)
Reworked toggling of the interface (using CSS animation)
Editing an item selects/highlights the entire text (like renaming files)
Ability to cancel edit via Esc key or button
Word wrapping of long item descriptions
Now escapes special characters in the item descriptions
Trims the string before adding or editing, avoids empty descriptions

In the front end:

Removed delete checklist functionality (since new checklist is generated upon refresh)
Moved remove item method from collection view to item view
So that item ids do not have to be stored in DOM
Fixed a bug where editing multiple items only picks the value of the first item being edited
Enforce hyphens for ids and classes, and single quotes for strings

Glass box front end testing on Chrome 40.0.2214. Quick tests for UI on Safari 8.0.2.

Toggling size works
Marking an item as done or undone works
Deleting an item works
Editing an item works
Cancelling item editing works
Adding an item works
Long text is wrapped
Special characters are escaped
Can edit multiple items without conflict
Whitespace in description is trimmed