Better printing of file size

If a file is 2.3GB, it will show up as 2300MB.  We should output it as 2.30GB instead, showing at least 3 significant digits.  But if it's less than a GB, it should show as 833MB.

See http://stackoverflow.com/questions/14488796/does-net-provide-an-easy-way-convert-bytes-to-kb-mb-gb-etc for a log based implementation.
