Error on unreplaced Upload scalar

[mike-marcacci]

This fixes #175.

[mike-marcacci]

It looks like more coverage is being requested, since the scalar file was previously untested (and now it's partially tested).

I won't have a chance to add the other tests today, but figured I'd get this PR in nonetheless.

[jaydenseric]

Great work for looking into this so quickly! I'm not sure when I'll be able to give it a detailed review, but just a quick thought: Should we use a TypeError? GraphQL.js is using it now, see graphql/graphql-js#1827.

[mike-marcacci]

I don't know how you can stay so up to date on all these things! I would have avoided using a TypeError on my own (since I most typically associate it with the wrong JS type being passed to a function) but I see that the ecosystem is using it here so I agree we should follow suit.

[jaydenseric]

Wouldn't this approach incorrectly error when the scalar is used correctly?

[jaydenseric]

I'm working on an alternative, really nice but more complicated solution: #181.