Choose correct protocol when using proxy

[mattfysh]

The req object is not replaced with the correct module (http/https) when a proxy is used. If the src.protocol changes when the following code is run, then the req object may not match what the original src.protocol was:

  if (process.env.HTTP_PROXY) {
    src = url.parse(process.env.HTTP_PROXY);
    src.path = this.assetUrl;
  }

This is in package.js.