Include Input types in response to introspection query.

[seanabrahams]

Why:

• Previously, the response to the full introspection query did not include Input types in its types list if they were arguments to an Input type. This became clear while working on graphql_relay as Relay relies on the result of the full introspection query which wasn't including all input types.

This change addresses the need by:

• While reducing types we needed a pattern match for %Input{} types to reduce their arguments.

[joshprice]

Looks good, thanks! 🚀 🚢