Handle localtunnel throwing error from ECONNREFUSED

Ref #755

This is actually an issue with browser-sync not handling the emitted error from localtunnel. Localtunnel will automatically attempt to reconnect the tunnel after this but if the error event is unhandled EventEmitter will throw the error, thereby crashing apps (e.g., say when using within a Gulp task).

I think this would be covered but simply binding to the error event within /lib/tunnel.js and maybe logging out the error? I have saved this from crashing by doing the following:

var inst = browserSync.init({
    proxy: 'localhost:4000'
  , tunnel: process.env.TUNNEL_SUBDOMAIN
  , open: !~process.argv.indexOf('--bg')
  , notify: false
  })

  inst.emitter.on('service:running', function() {
    inst.tunnel.tunnel_cluster.on('error', function(err) {
      if (!~err.toString().indexOf('firewall')) throw err
      log('Tunnel Reconnecting...')
    })
  })

BrowserSync / browser-sync

Handle localtunnel throwing error from ECONNREFUSED #823