Feature request - nfsiostat support

I will be completely honest, I'm sitting in a restaurant salivating thinking about getting back home and playing with this tool! The one thing that I have noticed that is missing that would make my life so much easier would be the inclusion of nfsiostat output support.

nfsiostat output is very similar to iostat, so it shouldn't be overly complicated to either tweak --iostat or create a new --nfsiostat command from the --iostat parser.

I'll come back and include some examples of the output to make your life a bit easier.

Thanks for creating this! Can't wait to get back home and check this out and kick the tires!