Make query diffing pluggable

Open discussion about if we should do query diffing.

One minor pro is it means we could remove graphql-js from the client build which would really lower our bundle size. https://github.com/apollostack/apollo-client/pull/153/commits/7a8dbec8d050bf095d6cff6606f289efc58c4d85 had to increase our size due to more exports from the graphql-js library.

[stubailo]

After talking to Jonas a bit, it would be cool if Apollo Client was almost a framework for writing the GraphQL client that you want - whether that’s diffing vs. not, runtime vs. build-time query parsing, etc - the basic architecture we have with redux lets us be pretty flexible about that.

There are only a couple of invariants to maintain - the API, the fact that you get the query results, etc - and the internals can be modified at will.

That would be a pretty awesome value prop for someone looking to use GraphQL in their client.

[jbaxleyiii]

@stubailo @helfer

After talking to Jonas a bit, it would be cool if Apollo Client was almost a framework for writing the GraphQL client that you want

Yes this, 💯 this

I would make things like building the embeddable apollo vs the full application one so easy to do