fix test

Author: LinXi

test/webpack.config.babel.js

@@ -1,7 +1,6 @@
 
 import path from 'path';
-import { Targets } from '../src';
-import WXAppWebpackPlugin from './plugin';
+import WXAppWebpackPlugin, { Targets } from '../src';
 
 const ext = process.env.TEST_EXT || 'js';