Reword README line about this being a dependency of Dealer, for clarity.

README.md

@@ -1,4 +1,4 @@
-This example package builds as part of our `Dealer` example:
+This example package will be cloned and built as a dependency if you build the `Dealer` example:
 
     git clone https://github.com/apple/example-package-dealer.git
     cd example-package-dealer