Are there many users of Protocols.HTTP.Promise already?

I made a less filling version, with slightly changed API. The new one is called Protocols.HTTP.Promise2 at the moment; if there are no objections, I'd replace HTTP.Promise with this one.

Most notable differences between HTTP.Promise2 and HTTP.Promise: a. Less filling (20% smaller compiled object file). b. Instead of two result objects, we simply have a single HTTP.Promise.Result object which is passed both on_success() and on_failure(). Why does the original separate this in a Promise.Success and Promise.Failure type? c. Various code optimisations, that do not change the interface. d. The Result object lacks the ok() method. What use was/is it? You should normally already know if you are a success or a failure callback. e. The Result object returns the raw body through "data", and the decoded body through get() (to conform more to standard Future objects).