Change getPorts to resolve all responses via promises to resolve race condition

[rikkuness]

Hopefully fixes #194

[gfwilliams]

Looks good, but it looks like:

          ports.sort(function(a,b) {
            if (a.unimportant && !b.unimportant) return 1;
            if (b.unimportant && !a.unimportant) return -1;
            return 0;
          });

got removed, or did you handle it somewhere else I missed? I think the unimportant thing is so the CLI can automatically connect to the correct device (it's not considering ones that probably aren't right).

[rikkuness]

good spot, I think I missed that, I'll fix now

[gfwilliams]

Great, thanks! Just merging