Feature Request: Query variables as a param

[ShMcK]

When using the schema tester, I was surprised to find that you can't pass variables in as a third param when using queries - you have to include the values in the query. Mutations take a third object param, just not queries.

I'd be happy to put in a PR if there are no objections.

[estrada9166]

Awesome! sure, a PR will be great!