Set destructors virtual to avoid surprises

lib/gesture/keyboard_swipe_gesture.h

@@ -44,7 +44,7 @@ namespace comfortable_swipe::gesture
         );
 
         // destructor
-        ~keyboard_swipe_gesture();
+        virtual ~keyboard_swipe_gesture();
 
         // hooks that we override
         virtual void begin() override;

lib/gesture/swipe_gesture.h

@@ -34,7 +34,7 @@ namespace comfortable_swipe::gesture
         swipe_gesture();
 
         // destructor
-        ~swipe_gesture();
+        virtual ~swipe_gesture();
 
         // fields for xdo
         int fingers;

lib/gesture/xdo_gesture.h

@@ -39,7 +39,7 @@ namespace comfortable_swipe
 
         public:
             xdo_gesture();
-            ~xdo_gesture();
+            virtual ~xdo_gesture();
         };
     }
 }