Formatted all pages according to guidelines.

pages/linux/usermod.md

@@ -1,15 +1,15 @@
 # usermod
 
-> Modifies a user account
+> Modifies a user account.
 
-- Change a user's name
+- Change a user's name:
 
 `usermod -l {{newname}} {{user}}`
 
-- Add user to supplementary groups (mind the whitespace)
+- Add user to supplementary groups (mind the whitespace):
 
 `usermod -a -G {{group1,group2}} {{user}}`
 
-- Create a new home directory for a user and move their files to it
+- Create a new home directory for a user and move their files to it:
 
 `usermod -m -d {{/path/to/home}} {{user}}`