Use of the default HTTP port when it's not present in the livereload.js URL

I use tiny-lr behind a HTTP reverse proxy which is listening the port 80. It's because I can only use some TCP ports on my company network.

So, I have this html in my webpage :
```html
<script src="http://myhost:80/livereload.js?snipver=1"></script>
```

Some browsers automatically change http://myhost:80/ to http://myhost/. So livereload.js doesn't detect the port and use 35729 by default. In my opinion, it could be better to use the default HTTP port.

This issue is related to this issue in grunt-contrib-livereload : 
https://github.com/gruntjs/grunt-contrib-livereload/issues/34

For information, here is my reverse proxy configuration with nginx 1.3.15 :
```
location /livereload {
	proxy_pass http://localhost:35729;
	proxy_http_version 1.1;
	proxy_set_header Upgrade $http_upgrade;
	proxy_set_header Connection "Upgrade";
}
```