selection needs to be restored on api changes

It may be the case the user's cursor is on a bold (or any other) blot
and an api call removes the format which would lose the selection.

Related #1152

core/quill.js

@@ -283,7 +283,9 @@ class Quill {
       [index, length, , source] = overload(index, length, source);
       this.selection.setRange(new Range(index, length), source);
     }
-    this.selection.scrollIntoView();
+    if (source !== Emitter.sources.SILENT) {
+      this.selection.scrollIntoView();
+    }
   }
 
   setText(text, source = Emitter.sources.API) {
@@ -394,7 +396,7 @@ function modify(modifier, source, index, shift) {
   let range = index == null ? null : this.getSelection();
   let oldDelta = this.editor.delta;
   let change = modifier();
-  if (range != null && source === Emitter.sources.USER) {
+  if (range != null) {
     if (index === true) index = range.index;
     if (shift == null) {
       range = shiftRange(range, change, source);