Changes v1.3.0
- Added firing a HeadGivenEvent when giving a head to a player (added so that other plugins can listen for this event (think about economy plugins charging for getting the head or making permissions to only get certain kinds of heads).

Changes v1.2.0
- Added the Category UI: "/headsinv cat" no longer gives a list of all categories, but opens an inventory UI that shows categories. Clicking the category automatically opens that category's UI.