Optimistic UI should work even when using a subscription

[cedvdb]

Optimistic UI should work with subscription

Currently you have to use watchQuery to be able to use optimistic UI. Having optimistic UI to work with subscription would be nice. However the watchQuery function doesn't accept a subscription (only query). The subscribe method doesn't listen to cache changes.

[hwillson]

To help provide a more clear separation between feature requests / discussions and bugs, and to help clean up the feature request / discussion backlog, Apollo Client feature requests / discussions are now being managed under the https://github.com/apollographql/apollo-feature-requests repository.

Migrated to apollographql/apollo-feature-requests#45.