Add a note about Backend handling of VoteOutcome's
Add initial API structure for leader callbacks
Add initial Completion implementation to Leader
Push Completion out to next layer of APIs, hiding it from Paxos users for now.
Convert ServerDispatcher to the new Leader completion API
Exposed Leader completion API to Paxos users.
Add a note to clean up VoteOutcome in context of AL events vs Leader Completion callbacks.
Merge branch 'master' of https://github.com/dancres/paxos