not found handler

[shakyShane]

Very basic for now, but doesn't interfere with the proxy.

The following will try to load a path from examples/basic/public, then from https://browsersync.io - if both give a 404, the 404 from the proxy will show

servers:
  - bind_address: 0.0.0.0:3000
    routes:
      - path: /
        dir: examples/basic/public
      - path: /
        proxy: https://browsersync.io

In this example though, the Browsersync UI will show for a 404

servers:
  - bind_address: 0.0.0.0:3000
    routes:
      - path: /
        dir: examples/basic/public