Added class and os alternates

.oh-my-zsh/plugins/perms/README.md

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+## Perms
+
+Plugin to handle some unix filesystem permissions quickly
+
+### Usage
+
+* `set755` recursively sets all given directories (default to .) to octal 755.
+* `set644` recursively sets all given files (default to .) to octal 644.
+* `fixperms` is a wrapper around `set755` and `set644` applied to a specified directory or the current directory otherwise. It also prompts prior to execution unlike the other two  aliases.