Make sure the driver is shutdown on Task#unregister!.

This appears to greatly reduce memory leaks on "god load".

lib/god/driver.rb

@@ -182,6 +182,13 @@ def initialize(task)
     def clear_events
       @events.clear
     end
+
+    # Shutdown the DriverEventQueue threads
+    #
+    # Returns nothing
+    def shutdown
+      @events.shutdown
+    end
 
     # Queue an asynchronous message
     #   +name+ is the Symbol name of the operation

lib/god/task.rb

@@ -299,7 +299,7 @@ def register!
     end
 
     def unregister!
-      # override if necessary
+      driver.shutdown
     end
 
     ###########################################################################

lib/god/watch.rb

@@ -177,6 +177,7 @@ def register!
 
     def unregister!
       God.registry.remove(@process)
+      super
     end
   end