Implement `quit' action keyword

lib/uh/wm/actions_handler.rb

@@ -0,0 +1,17 @@
+module Uh
+  module WM
+    class ActionsHandler
+      def initialize env, events
+        @env, @events = env, events
+      end
+
+      def evaluate code
+        instance_eval &code
+      end
+
+      def quit
+        @events.emit :quit
+      end
+    end
+  end
+end