Use "error" status when there is a compile error

[ErikSchierboom]

When testing the Elm test runner, I found one small issue. In the case of a compilation error, the root "status" field is set to "fail", but instead in this case it should be set to "error" (see https://github.com/exercism/automated-tests/blob/master/docs/interface.md#top-level).

[mpizenberg]

Ah thanks Erik and Jeremy!