Added RiakCS Support

Fixes issue #1100 

This is my first DD check, please feel free to speak of it harshly.

Tested in Centos 6.5 so far.
Would these proxy settings be the same as the agent proxy settings (https://github.com/DataDog/dd-agent/blob/master/datadog.conf.example#L7-L10) ?

If so we should probably use them (they are stored in self.agentConfig)