Allow batch requests

The attached three commits allow for performing batch requests against Linode's API.

The first commit simple factors the response parsing of the data structure returned out to a different sub than the HTTP::Response parsing sub.

The second commit actually adds base object methods for queueing requests. sending queued requests, and managing the queue (minimally).

The last two commits extends the batch processing capabilities over the mapped Linode API methods, allowing QUEUE_ to prefix any mapped API method to queue it for later processing, and adds a new method to lowercase the keys of batch responses.