New input plugin: logstash-input-qingstor

Hi:
I would like to contribute https://github.com/Tacinight/logstash-input-qingstor.
[Qingstor](https://www.qingcloud.com/products/storage#qingstor) is a object storage service provided by [Qingcloud](https://www.qingcloud.com/). It functions just alike s3 and so are their source codes (pls forgive me for I'm just a ruby newbie ^_^). I also developed it's twin output plugin:
https://github.com/Tacinight/logstash-output-qingstor
I would open another issue for this output plugin and hope it won't bother you.

Best wishes.