Support IPAddress

[Timontheweb]

Please can you add class IPAddressCommandLineOptionParser? I've forked and added it, but it really is so simple it would probably be easier for you to add it directly :)

Thanks!

[jzabroski]

@Timontheweb This is what pull requests are for.

[siywilliams]

Indeed a pull request would be much easier ! :)