Specifying the Node project directory with webpack dev middleware #262

I would like to be able to specify the Node project path when using webpack dev middleware to allow Javascript apps to be included from any location e.g.

Host/
  project.json
  Startup.cs
  Program.cs
App/
  package.json
  webpack.config.js
  src/
  node_modules/

At the moment it can't be changed from the content route. I've made what look like the necessary changes in a fork, but ran into another issue packaging the library before I could try it out. Happy to create a pull request if this is deemed useful enough.