Handles ports for SW.

[paullewis]

SW check needs ports.

Fixes #532

[paulirish]

If you're up for it we could use whatwg-url package to normalize our url parsing everywhere.
It can also be added to our browserify excludes.

Here's it in action:

https://tonicdev.com/5798e3b9edc3e41200aaa828/5798f15349cba51300e86a05

[wardpeet]

For the few times we use url parsing I wouldn't introduce a new dependency

[paullewis]

I'm undecided. Browserify already polyfills node's URL parsing IIRC, so we're consistent if less good than I'd like. I kinda agree with @wardpeet about not introducing a new dep at this stage, though as these things go it's pretty small and that.

[brendankenny]

@zhaoz would have to update for this dep too, and he just got done with all that :)

[paulirish]

Aiight. sg.