More specific autoloading dir

doc/01-basic-usage.md

@@ -165,7 +165,7 @@ Composer will register a
 autoloader for the `Acme` namespace.
 
 You define a mapping from namespaces to directories. The `src` directory would
-be in your project root. An example filename would be `src/Acme/Foo.php`
+be in your project root, on the same level as `vendor` directory is. An example filename would be `src/Acme/Foo.php`
 containing an `Acme\Foo` class.
 
 After adding the `autoload` field, you have to re-run `install` to re-generate