Can README clarify the necessary elements for specs to run in order?

[amcaplan]

I spent basically all of today trying to figure out how to get apivore specs to run in the appropriate order so the grand-finale spec will pass.

For future developers, it might help to clarify that:

1. The grand-finale spec has to go last
2. It's necessary to specify order: :defined on the top context
3. You can't define specs in other files (unless you include them via shared_examples)
4. The and context is actually necessary because of RSpec's recursive method of spec ordering

Won't help me at this point, but it might make future devs' intro to apivore a little smoother.

Also, thanks so much for this awesome tool! Despite my rough intro, it's saving our team a lot of time and giving us much greater confidence that our API actually matches the docs we've set up for it.