Set initial annotation counts to 0 because annotation counters are not updated...

Set initial annotation counts to 0 because annotation counters are not updated if a page has no annotations.

src/annotator/annotation-counts.js

@@ -13,6 +13,8 @@ var ANNOTATION_COUNT_ATTR = 'data-hypothesis-annotation-count';
  */
 
 function annotationCounts(rootEl, crossframe) {
+  updateAnnotationCountElems(0);
+
   crossframe.on(events.PUBLIC_ANNOTATION_COUNT_CHANGED, updateAnnotationCountElems);
 
   function updateAnnotationCountElems(newCount) {