End-to-end run of iterations is not working

When trying to submit an iteration, the status does not change from pending. After some digging, the cause was [this PR](https://github.com/exercism/tooling-orchestrator/pull/13) to the tooling-orchestrator, which enables tooling to output multiple files. Unfortunately, the other tooling bits (invoker and webserver) need to be updated to accomodate this changed interface.