Update 2.0-migration: add afterware example about authenticating via headers (#2554)
Update 2.0-migration: add afterware example about authenticating via headers (#2554)

Because with apollo link getting headers in the response is quite different from the previous version.
apollostack/apollo-client,apollographql/apollo-client,apollostack/apollo-client,apollostack/apollo-client,apollographql/apollo-client