Only unbind events passed from the parent component (#613)

`initEchartsInstance` attached a handler for the `"finish"` event. If
`componentDidUpdate` is called between attaching the handler, and firing
the handler and the `onEvents` prop changed, this will fire
`"offEvents"` which will remove the handler for the `"finish"` event.
This means the finish handler never fires, so the chart auto-resize is
not attached, and the ready event handler never fires.

Instead, only remove the events that are on the previous props, and
leave the `"finish"` callback alone.

Author: gggritso

src/core.tsx

@@ -190,7 +190,7 @@ export default class EChartsReactCore extends PureComponent<EChartsReactProps> {
     // loop and off
     for (const eventName in events) {
       if (isString(eventName)) {
-        instance.off(eventName);
+        instance.off(eventName, events[eventName]);
       }
     }
   }