Nag based on task state before modification

With this patch, taskwarrior uses the urgency of tasks before any
modifications are applied when deciding whether to show nag messages.

Previously, taskwarrior would apply modifications before deciding
whether to show nag messages, which could lead to spurious nag messages
when completing an active task.

src/main.h

@@ -48,7 +48,7 @@ void updateRecurrenceMask (Task&);
 void handleRecurrence2 ();
 
 // nag.cpp
-bool nag (Task&);
+void nag (std::vector <Task>&);
 
 // rules.cpp
 void initializeColorRules ();