docs: Make schema directive example clearer (#1715)
docs: Make schema directive example clearer (#1715)

The schema directive example [here](https://www.apollographql.com/docs/apollo-server/v2/features/directives.html) doesn't work. The package being imported was meant to be an _example_, unworking directive. This is confusing for people trying to run this example, so I replaced it with a real one.
apollostack/apollo-server