Added support for tickets endpoint

Author: Tommy Lacroix

README.md

@@ -216,6 +216,10 @@ Returns single ticket item for the given `id`.
 
 Create a ticket.
 
+#### api.tickets.tags(id, parameters, callback)
+
+Update tags of a single ticket item for the given `id`.
+
 ### Visitors
 
 ### api.visitors.list(callback)