On the main README, the compatibility API is listed as the third feature, and there's a whole section on how wonderful it is (which it is): "That's right, you can just replace "require 'json'" with the line above and you're done!"
But when you actually use it, you get an ugly deprecation error. If the feature is being deprecated and removed, the README should reflect that, and not advertise the feature...
Good call, I missed that in the master branch. It's already been updated in the 2.0 branch, I'll try and fix it when I get home later.
So, as you are probably deprecating the JSON compatibility API, how about fixes for it? I noticed the typo compatability instead of compatibility in several places. Problem is that it appears in a method name, so the old method should be printing a warning. If you would like I could make a PR, just let me know.