Clarified kata requirements and fixed tests for conjured items.

[k-hoszowski]

In the repo this was taken from, namely https://github.com/istepaniuk/gilded-rose-js-with-tests it says:

Note that this Kata has been slightly modified from the original by Terry Hughes and Bobby Johnson. Namely, in the original Kata the Brie Cheese does not behave exactly like the Backstage passes as this code does.

This should be indicated in this repo as well. I also noticed that tests for conjured items were the wrong way around: the quality is being deducted twice as fast in the wrong test. Because of this change, the unskipped test will return an error for the starter code. It can be commented out, but perhaps there's a better way I don't know.