Document impact of starting populated world

Change-Id: If9c286b1351cb1f7680b778ba04c334f6ef23396

qml/Gravity.qml

@@ -80,6 +80,7 @@ Item {
                 id: columnWorld
 
                 timeStep: d.pace
+                // There is less item fall through when this runs perpetually
                 running: d.running
             }
 

qml/main.qml

@@ -12,7 +12,7 @@ Window {
 
     Settings {
         id: settings
-        property int itemTravel: 2
+        property int itemTravel: 1
         property int columnCount: 30
         property int interval: 2
         property bool fitByHeight: false