Merge pull request #30 from benmills/master

Refactor peer communication into broadcast
Followers persist state before appending entries.
Update voter to persist state before respond to RequestVote rpc
Adds integration test for loading state from disk.
Elected server heartbeats after successful election.
Merge pull request #31 from wjdix/master

Adds integration test for loading state from disk.
Refactor sending of heartbeat.
Merge pull request #32 from wjdix/master

Refactor sending of heartbeat.
Remove examples from candidate tests.