Added an event that other developers can listen to called ShopSignEvent
will make a javadoc for it later.
contains methods for getting the players uuid, the item, amount, price, location and if it's buying/selling. you can also cancel the even.

People updating to this one, please add
transactionFailed: "[PREFIX] &cTransaction failed."
to your lang.yml if you want to be able to edit it. it's for when other plugins cancel the event.