Sizes not working on dev and master branches

[lpanebr]

betty whats the size of:

$ betty whats the size of ~/Dropbox
1.05 MB    1102408  /home/lpanebr/Dropbox

$ du -sch ~/Dropbox
1.1G    /home/lpanebr/Dropbox
1.1G    total

[trizen]

I already sent a pull request. The fix would be to add -h for du. See: https://github.com/trizen/betty/blob/dev/lib/sizes.rb