raft: add test for findConflict
raft: comments for isUpToDate
raft: refactor isUpToDate and add a test
raft: use raft-specific rand.Rand instead of global one
Merge pull request #1432 from unihorn/187

raft: use raft-specific rand.Rand instead of global one
raft: address issues in comments
Merge pull request #1419 from xiangli-cmu/raft_log_test

raft: add test for findConflict
error: write->writeTo
Merge pull request #1436 from xiangli-cmu/writeTo

error: write->writeTo
etcdhttp: make admin HTTP endpoint return json format error