90bfa03 Improve `dep-tree` command.

Authored and Committed by kapstok a year ago
    Improve `dep-tree` command.
    
    * Implement 'Display' Trait.
    * Able to process `dep-tree` arguments.
    * Restructure 'OS' enum in 'system.rs' module.
    
        
file modified
+0 -1
file modified
+8 -14
file modified
+47 -19
file modified
+1 -0
file modified
+13 -2