Re-export everything from apollo-client

[bensalilijames]

Fixes #521. :)

TODO:

• If this PR is a new feature, reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• Update CHANGELOG.md with your change
• If this was a change that affects the external API, update the docs and post a link to the PR in the discussion

[apollo-cla]

@benhjames: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Meteor Contributor Agreement here: https://contribute.meteor.com/

[thebigredgeek]

@helfer lgtm. thoughts?

[helfer]

Will that export the default as ApolloClient? We should make sure that's the case. Otherwise we should just list all the things that we want to export. It's okay if there are a few things missing occasionally, because people can always import directly from apollo-client as a workaround.

[bensalilijames]

ApolloClient is also a named export from apollo-client (as well as the default export) so it should make no difference.

Ref: https://github.com/apollographql/apollo-client/blob/master/src/index.ts#L121

[helfer]

Ok, I'm convinced.