Use webpack options sockPath, sockHost, and sockPort to get socket URL

[mefu]

Hello,

This pull request fixes issue #41.

I looked at entry files of webpack-dev-server and webpack-hot-middleware to understand how can I pass variables to entry scripts.

Right now, I just check if ___resourceQuery exists, and parse it instead of this. It worked well in my tests of 3 considerably big and complex reactjs projects but I cannot claim that I've tested every possible webpack configuration.

If you provide feedback, I will implement it.

Thank you!

[gregberge]

Thanks!