in-memory resources are not loaded after proxy bypass

[skwakman]

When using proxy's bypass function, resources that are bypassed and are part of the in-memory webpack bundle are not retrieved. Instead, only files from the filesystem are retrieved.

Example:
Running the server using --inline

proxy: [{
  context: ['**'],
  target: 'http://someOtherServer:1234/',
  bypass: function(req, res, proxyOptions) {
    if (req.url.indexOf('clientlib-all.js') != -1) {
      return '/bundle.js'; // this file is part of the webpack bundle and should be loaded from memory, but it's not. Instead it returns a 404 _or_ if the file exists on the file system, that one is loaded instead.
    }
    return false;
  }
}];

I've fixed this locally by manually editing webpack-dev-server's Server.js file:

// ... line 269
    var defaultFeatures = ["setup", "headers", "middleware"];
    if(options.proxy)
        defaultFeatures.push("proxy"); // add a second parameter with value "middleware" to this .push call and it works
// ...

webpack: tested with 1.13.2, although bug is in server, not in webpack itself
webpack-dev-server: confirmed on 1.16.1 but might also be present in 2.x
OS: OSX 10.11.6, local installation

[SpaceK33z]

PR welcome.

[skwakman]

Can this fix also be merged for the 1.x branch?