警告如下：

npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules\chokidar\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.0.17: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN vue-loader-demo@1.0.0 No description
npm WARN vue-loader-demo@1.0.0 No repository field.

原因是因为： fsevent是mac osx系统的，在win或者Linux下使用了 所以会有警告，忽略即可。意思就是你已经安装成功了。。。