Feature/inverted tree

[solidiquis]

Additions

• Total bytes now shown by default with --human flag provided as option to show human-readable disk usage.
• Tree now prints with root directory at the bottom by default to make it quick to see total size of root. --inverted option is provided for traditional tree view.

-H, --human                      Print disk usage in human-readable format
--inverted                   Print tree with the root directory at the topmost position