Annotation arrows can now be placed using absolute paper coordinates

Author: nicholas-esterer

src/components/annotations/defaults.js

@@ -60,8 +60,7 @@ function handleAnnotationDefaults(annIn, annOut, fullLayout) {
         if(showArrow) {
             var arrowPosAttr = 'a' + axLetter;
             // axref, ayref
-            var aaxRef = Axes.coerceRef(annIn, annOut, gdMock, arrowPosAttr, 'pixel',
-                    undefined, true);
+            var aaxRef = Axes.coerceRef(annIn, annOut, gdMock, arrowPosAttr, '', 'paper', true);
 
             // for now the arrow can only be on the same axis or specified as pixels
             // TODO: sometime it might be interesting to allow it to be on *any* axis