Apollo-server: Support for 64 bit int

[tonyxiao]

I'm getting this error when returning a large number from apollo server

      "message": "Int cannot represent non 32-bit signed integer value: 2303492096",

Initially I thought it's an issue with GraphQL, but seems that it's actually related an implementation level thing.
https://github.com/facebook/graphql/issues/73

[stubailo]

It's a graphql-js thing - both apollo server and graphql tools are based on graphql-js, Facebook's reference implementation.