Error out when unsupported keys are supplied

[papandreou]

I just accidentally did this:

expect(..., 'with http mocked out', [
    ...,
    { url: 'DELETE http://foo.bar/quux' },
    ...
], ...);

Which should have been { request: { url: 'DELETE http://foo.bar/quux' } }. It was interpreted to mean "here any request should happen, I don't care what it looks like, just reply with a 200".

Let's go through it and ensure that we error out when any unsupported property is passed, sort of like https://github.com/unexpectedjs/unexpected-express/blob/master/lib/unexpectedExpress.js#L171-L176