Update README: clarify versions

Author: Vince Varga

README.md

@@ -16,7 +16,7 @@ A powerful Http client for Dart, which supports Interceptors, Global configurati
 dependencies:
   dio: 3.x #latest version
 ```
-> In order to support Flutter Web, v3.x was heavily refactored, so it was not compatible with version 3.x See [here](https://github.com/flutterchina/dio/blob/master/dio/CHANGELOG.md) for a detailed list of updates.
+> In order to support Flutter Web, v3.x was heavily refactored, so v3.x is not compatible with v2.x See [the changelog](https://github.com/flutterchina/dio/blob/master/dio/CHANGELOG.md) for a detailed list of updates.
 
 ### Super simple to use