Check that candidate's log is up to date during election

[amidvidy]

When granting a vote,we are currently missing the check to see if the candidate's log is
at least as up-to-date as the voter's log. The following condition must be met
in order to grant a vote:
req.lastLogTerm > voter.lastLogTerm ||
(req.lastLogTerm == voter.lastLogTerm &&
req.lastLogIndex >= voter.lastLogIndex)

Thanks to Diego for pointing this out.