laravel4: add README (#7220)

plugins/laravel4/README.md

+# Laravel 4 plugin
+
+This plugin adds some aliases for common [Laravel 4](https://laravel.com/docs/4.2) commands.
+
+To use it, add `laravel4` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... laravel4)
+```
+
+## Aliases
+
+| Alias | Command                                   | Description                                     |
+|-----------|-------------------------------------------|-------------------------------------------------------------|
+| la4       | `php artisan`                             | Main Artisan command                        |
+| la4dump   | `php artisan dump-autoload`               | Regenerate framework autoload files         |
+| la4cache  | `php artisan cache:clear`                 | Flush the application cache                 |
+| la4routes | `php artisan routes`                      | List all registered routes                  |