Merge pull request #42 from phwoolcon/master

test: fix phpunit 6 compatibility issue

Merge pull request #38 from Liv1020/master

增加names的get方法，使其拥有更好的扩展

Fixed typo

Fixed a notice

Fixed #33

Improved wrap, all, any and settle

Update co2.php

Fixed Promise\promisify

Added response httpHeader support for http client

Improved retry.