Add file upload test, handle upload in koa integration

[HriBB]

OK, so this time the changes are more transparent. I think something got screwed up with the number of spacings.

I added a failing test to integrations.test.ts and a very naive file upload implementation to koa integration.

@helfer please review

TODO:

• Update CHANGELOG.md with your change (include reference to issue & this PR)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass

[helfer]

Oh, sorry, I think maybe I didn't describe clearly in the other PR: It would be great if you could separate the PR into two: one to add the failing test, then another one (on top of the first PR) which implements file upload against Koa.

Since we don't want to have failing tests on master I created a new branch against which you can make the PR: file-upload. That way we can merge the PR onto that branch and also make the HAPI, Koa and express PRs against it to get all the tests to pass before we merge into master.

Sound good?

[HriBB]

Ahh OK I get it now. Did not read your instructions properly. Will fix it tomorrow.

[HriBB]

Closing this PR, will continue in file-upload branch.