Add batcher module and Message object

Add the batcher process module with the Message object that wraps tasks
inserted into the pull queue.
Add queue.yaml with default and defualt-pull entries.

Also update the batcher module to use the defualt-pull queue by default.
Remove unneeded comment in batcher unit test.
Merge pull request #18 from beaulyddon-wf/add_batcher

Add batcher module and Message object