Rackspace CDN methods

Thought we could continue the discussion from #87 here @indexzero. I got all the container methods working fine, just ran into a hiccup with the upload/download methods due to how I have to get the storageUrl. I'll look into how I can extract the buffering code from the `base.Client.request` method to be able to reuse that for the upload/download. @cronopio any ideas? I just wanted to get some eyes on the code in the mean time. Let me know what you guys think.

Tests/Docs will also be forthcoming.