Add note clarifying intent for package

ssfinney · ssfinney · commit 5fbd1ea0dc3b · 2019-12-03T10:03:54.000-05:00
diff --git a/readme.md b/readme.md
@@ -18,7 +18,7 @@ PHPUnit mail assertions for testing email in Laravel.
 
 ## Installation
 
-Install the package:
+Install the package inside your dev dependencies:
 
 ```bash
 $ composer require spinen/laravel-mail-assertions --dev
