Allow turning off rollingMode via setOptions()

Turning it on via setOptions() already worked but not the opposite.
fixes #939

Author: bpfoster

lib/timeline/Range.js

@@ -109,11 +109,16 @@ export default class Range extends Component {
       ];
       util.selectiveExtend(fields, this.options, options);
 
-      if (options.rollingMode && options.rollingMode.follow) {
-        this.startRolling();
-      }
-      if (options.rollingMode && options.rollingMode.showButton && !this.rolling) {
-        this.body.dom.rollingModeBtn.style.visibility = "visible";
+      if (options.rollingMode) {
+        if (options.rollingMode.follow) {
+          this.startRolling();
+        } else {
+          this.stopRolling();
+        }
+
+        if (options.rollingMode.showButton && !this.rolling) {
+          this.body.dom.rollingModeBtn.style.visibility = "visible";
+        }
       }
       if ('start' in options || 'end' in options) {
         // apply a new range. both start and end are optional