找不到模块“ babel-core”中的错误。使用react.js，webpack和express服务器

每当我webpack在终端上运行时，我都会得到：

Hash: efea76b1048c3a97b963
Version: webpack 1.12.13
Time: 33ms
    + 1 hidden modules

ERROR in Cannot find module 'babel-core'

这是我的webpack.config.js文件

module.exports = {
  entry: './app-client.js',
  output: {
    filename: 'public/bundle.js'
  },
  module: {
    loaders: [
      {
        exclude: /(node_modules|app-server.js)/,
        loader: 'babel'
      }
    ]
  }
}

package.json

{
  "name": "react",
  "version": "1.0.0",
  "description": "React polling app",
  "main": "app-client.js",
  "dependencies": {
    "babel-loader": "^6.2.2",
    "bootstrap": "^3.3.6",
    "express": "^4.13.4",
    "react": "^0.14.7"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}