nextIndex when sending entries to replicas was off by one

as per fig.2 in raft paper, nextIndex for each follower is the value of next index in log to send.
Was previously set to be same as matchIndex which is last index known to have been sent to follower
also simplified running to be a boolean instead of an int
Merge pull request #75 from foldlabs/next-index-off-by-one

nextIndex when sending entries to replicas was off by one