title: lua http.request return attempt to index global 'http' (a nil value)
body: <p>I just try simple lua code:</p>
  
  <pre><code>local http = require("socket.http")
  local  b, c, h = http.request("http://www.example.com/")
  </code></pre>
  
  <p>But I get this error:</p>
  
  <pre><code>stdin:1: attempt to index global 'http' (a nil value)
  stack traceback:
          stdin:1: in main chunk
          [C]: ?
  </code></pre>
  
  <p>luasocket is installed and lua find it, anyone can help?</p>