use diffrent units for different file sizes fixes #61

[ducaale]

No description provided.

[k0pernicus]

Hello @ducaale, thank you for this PR.
Actually, I think we can improve the code.

I think that each file has to be tagged with an enum (KB, MB, GB, etc...), and we have to derive Debug and Display for those enums to print out those.
You can maybe implement this code in a new module (filesize.rs for example), and use it in main.rs to display it...

[k0pernicus]

Really great :-)
Thanks a lot !