retains port info for local siteurl

Firstly, thanks for making this plugin. I've been taking over some WP projects lately, coming from Rails/Python, and have been frustrated by how manual everything is. Am working on automating deployment, so loving this plugin.

My use case might be niche. I've been using a Vagrant VM as my local development Wordpress server, which has VM port 80 mapped to my computer's port 8080. As such, my site urls for local dev are http://localhost:8080.

Running wp deploy push staging strips the port before search-and-replace, so my staging URLs look like http://domain/sub-domain:8080/. I wanted to fix this.

The port-stripping happens in helpers.php, in the trim_url function, when the url is parsed, and only the domain is retained. Link here.

I forked the repo and kept the port for my own purposes. Currently, I've hardcoded to always keep port info, but could easily move it do a config param. I've opened this PR to show you what I mean. Feel free to close the issue without merging if you don't think it's a big deal.

Cheers