update: 升级element版本

package.json

@@ -46,7 +46,7 @@
     "clean-webpack-plugin": "^0.1.19",
     "copy-webpack-plugin": "^4.0.1",
     "css-loader": "^0.28.0",
-    "element-ui": "^2.4.3",
+    "element-ui": "^2.15.6",
     "extract-text-webpack-plugin": "^3.0.0",
     "file-loader": "^1.1.4",
     "friendly-errors-webpack-plugin": "^1.6.1",