auto-configure routes for static websites

[Nowaker]

GitHub static pages can be delegated to a custom domain by adding a CNAME to root directory. We could recognize the CNAME file placed in the root of static website and auto-configure http-master.

Currently it looks like:

{
  "443": {
    "static": {
      "example.com": "/home/example.com/public"
    }
  }
}

It could be reduced to:

{
  "443": {
    "static": [
      "/home/example.com/public"
    ]
  }
}

Additionally, if we pass the port number in file called PORT file in the root directory, this is all we need:

{
  "static": [
    "/home/example.com/public"
  ]
}

I'm not sure how it plays with your ideas for future (the user-friendly config), but the idea is simple: read CNAME and PORT files and configure the http-master accordingly.