Reset onload flag when recalculate called

This ensures sticky elements don't fade in if
in a sticky position when the page loads.

The fade is there to show when an element is
becoming sticky. This has no use if it was already
sticky the first time you see it.

Because the same situation applies when
recalculate is called, we also want the flag to be
reset before this happens.

app/assets/javascripts/stick-to-window-when-scrolling.js

@@ -462,6 +462,9 @@
     }
 
     if (numOfEls) {
+      // reset flag marking page load
+      this._initialPositionsSet = false;
+
       $els.each(function (i, el) {
         // delay setting position until all stickys are loaded
         self.add(el, false, onLoaded);