Category Theory for Promises/A+

I think this is a really important post, and I hope the suggestions are implemented. This will give Promises in JS a clean and simple API.

The current proposed API is full of corner cases, justified on the basis that providing a single method, `then`, is simple. Unfortunately this is too simple, hence the corner cases.

Unfortunately it seems the people in charge of the promise spec are not open to change, or even to rational argumentation. If you want to see some really pathetic behavior read this thread: https://github.com/promises-aplus/promises-spec/issues/94