Implemented "Clear Traces" tool

Readme.md

@@ -19,7 +19,7 @@ TODO
 - [ ] Zoom Easing
 - [ ] 2-touch Pan & Zoom
 - [ ] Multi-touch Mass Create
-- [ ] Tool to Clear Traces
+- [x] Tool to Clear Traces
 - [ ] Undo feature: 
   - [ ] Undo "Clear Traces" Action
   - [ ] Undo "Reset

tool/play-pause.js

@@ -87,5 +87,12 @@ export class PlayPause extends Tool {
         this.updateButtons();
       }
     });
+
+    clearTraces.addEventListener('click', () => {
+      // Obliterate object histories
+      this.sim.objects.forEachObject(obj => {
+        obj.history = [];
+      }, null);
+    });
   }
 }