Support asynchronous events; Addresses BUKKIT-1212

By: Wesley Wolfe <weswolf@aol.com>

paper-api/src/test/java/org/bukkit/event/TestEvent.java

@@ -0,0 +1,19 @@
+package org.bukkit.event;
+
+
+public class TestEvent extends Event {
+    private static final HandlerList handlers = new HandlerList();
+
+    public TestEvent(boolean async) {
+        super(async);
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}