Add expectBody option and related tests

[doesdev]

This is probably a niche need driven by my paranoia. However, for certain scenarios it adds peace of mind knowing that the server sent what I expected it to back to the client. While this isn't necessarily the place of a benchmarking tool, it is helpful to me to have this for stress testing sorts of purposes.

I understand if it doesn't fit. That being said it's mostly an unobtrusive addition. The only thing it really imposes is the addition of mismatches to the API results. I suppose I could have fenced that off so that it only shows in the results if the option is enabled. Let me know if that would be desirable and I can do that.

[mcollina]

I think this would be helpful in a few cases.

Can you make this throw if the requests option is set? These two will be uncompatible.

We might also want to add expectHeaders and expectStatusCode.

[doesdev]

Awesome, thanks for the quick feedback. I've added the error and related test as well as that warning. Good call on expectHeaders and expectStatusCode. Those will be nice to have as well. Will work on those over the next couple days here.

Do you think for the API results those 3 options should all share the mismatches count or should there be a prop for each of them? Was thinking it might be a good bit of noise to have 3 separate properties added to the results, but whichever way you think would be best.

[mcollina]

LGTM