Support for 64 bit int

[tonyxiao]

Initially I thought it's an issue with Apollo server,

apollographql/apollo-server#145

But on second thought maybe it's graphql-tools.

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.
graphql/graphql-spec#73

[stubailo]

It's a graphql-js thing: https://github.com/graphql/graphql-js