Feature: Base 2 output (Gi, Mi, Ki)

[DavidEichmann]

The output currently uses base 10 (e.g. K means Kilobyte = 1000 byte). Measurements from GHC such as the output from -Dg are measured in base 2 e.g. KiB = 1024 byte. I'd like an option to output base 2 units so that I can better compare with GHC measurements.

https://physics.nist.gov/cuu/Units/binary.html