Requests 2.6.0 发布

Requests 2.6.0 发布，此版本现已提供下载：https://github.com/kennethreitz/requests/archive/v2.6.0.zip。

更新内容如下：
**Bug 修复**
Fix handling of cookies on redirect.
Fix error when requests is an install_requires dependency and python setup.py test is run. (#2462)
Fix error when urllib3 is unbundled and requests continues to use the vendored import location.
Include fixes to urllib3's header handling.
Requests' handling of unvendored dependencies is now more restrictive.

**新特性和改进**
Support bytearrays when passed as parameters in the files argument. (#2468)
Avoid data duplication when creating a request with str, bytes, orbytearray input to the files argument.

更多内容请看https://github.com/kennethreitz/requests/blob/master/HISTORY.rst。