[boost] Promise/A+ like javascript in cpp

Hi, Javascript Promise creates a task chain to help develop asynchronized application with single thread. I did not find a good implement of this kind of "Promise" in c++, so i create one named "promise-cpp" here -- https://github.com/xhawk18/promise-cpp with which, we can write asynchronized tasks like sequential flows. Here's an example of promisifed http client in boost::asio -- https://github.com/xhawk18/promise-cpp/blob/master/test/asio_http_client.cpp "promise-cpp" would be the best friend to boost::asio's asynchronized task for single thread, and it is not std::promise. Thanks for you reviewing this library and any suggestion will be appreciated!