tui: Allow handlers to finalize() as well as initialize()

kittens/tui/handler.py

@@ -5,11 +5,23 @@
 
 class Handler:
 
-    def initialize(self, screen_size, quit_loop, wakeup, start_job):
+    def _initialize(self, screen_size, quit_loop, wakeup, start_job):
         self.screen_size, self.quit_loop = screen_size, quit_loop
         self.wakeup = wakeup
         self.start_job = start_job
 
+    def __enter__(self):
+        self.initialize()
+
+    def __exit__(self, *a):
+        self.finalize()
+
+    def initialize(self):
+        pass
+
+    def finalize(self):
+        pass
+
     def on_resize(self, screen_size):
         self.screen_size = screen_size