- Conditions that check whether the SI or IEC units must be used were
  inverted, i.e., when `si_prefix == true` it would use `"iB"` instead of
  `"B"`.
- KB & kiB were used instead of kB & KiB.
- Switches (true/false) in tests are also fixed.

Additional small fixes:
- Removed comment about fixed bug in `./src/lib.rs`.
- Rust code now has consistent 4 spaces indents in README.md.