add option to serve on specific address

This adds `ionic serve --address XYZ` to `ionic serve`.

When you `ionic serve`, you potentially get a prompt asking you which address to use, making it unsuitable for scripting (e.g. when inside a vagrant provisionier, or just a convenience script to prepare your coding session).

With `--address`, you now get a specific address, e.g. `ionic serve --address localhost --port 6543`, xor a program failure.