title: "npm run build:css " can not work, while it is ok when I run the script self
body: <p>I am doing a program, I meet some question when I use the npm script with Mac system;<br>
   I have already install the node-sass globally, the package.json file is as follows: <a href="http://i.stack.imgur.com/YI4gW.png" rel="nofollow">package.json</a><br>
  it is not work when I run "npm run build:css",while the error the system tell me is as the follow picture:
  <a href="http://i.stack.imgur.com/l8qsg.jpg" rel="nofollow">the err discription</a>
  <strong>but</strong> I can run the commend <code>node-sass ./src/scss/pages/index.scss ./static/css/index.css</code> successfully in the terminal and if I add another line like <code>"create":"touch sun.js"</code> to package.json, it works well when I run <code>npm run create</code>; </p>
  
  <p>I am confused, I will be grateful if someone can give some suggestion. </p>