Have rsync output numbers in a human-readable format

It's only minor but I've started using this to make the output of the bootstrapper a little more friendly when dealing with larger changes.

For example:

    sent 86451 bytes  received 298 bytes  173498.00 bytes/sec
    total size is 177305  speedup is 2.04

Becomes something like:

    sent 86.44K bytes  received 292 bytes  173.47K bytes/sec
    total size is 177.31K  speedup is 2.04