title: run webpack with command line args
body: <p>I've been trying to pass args from command line to webpack plugin.
  I can access the args via process.argv but after that wwebpack fails with error:
  ERROR in Entry module not found: Error: Cannot resolve module
  It seems that webpack treats the args as folders it needs to find.
  This is how I pass the args:
  webpack accessKey=myKey</p>
  
  <p>Resolved:</p>
  
  <p>Saw two ways of doing this:</p>
  
  <ol>
  <li><p>Add the param before calling webpack and use the process.env. to access it:
  For example : myparam=1231 webpack 
  in the webpack config file:
  process.env.myparam == 1231</p></li>
  <li><p>Add the args after the webpack command as flags using --.
  For example : webpack --myparam
  in the webpack config file: process.argv[2] == --myparam</p></li>
  </ol>
  
  <p>Hopes this helps</p>