Fix small bug in web UI and minor clean-up.

There was a bug where sorting order didn't work correctly for write time metrics.

I also cleaned up some earlier code that fixed the same issue for read and
write bytes.
Merge pull request #227 from pwendell/master

Fix small bug in web UI and minor clean-up.

There was a bug where sorting order didn't work correctly for write time metrics.

I also cleaned up some earlier code that fixed the same issue for read and
write bytes.