PowerMessage is no longer being maintained. Instead, you can make use of the newer, more up-to-date messages API present in Commodus (based on PowerMessage), first drafted in this commit. The newer API facilitates similiar functionality to this library with in-built support for SpongeAPI.
Note: if you are using PowerMessage in a plugin built purely for Bukkit, it will still work just fine :).
Modification of Fanciful by mkremins
Allows the sending of cool, interactive messages to player clients through internal manipulation of JSON. Plugins using this don't have to worry about any of that though :3