raft: include commitIndex in heartbeat
Merge pull request #1737 from xiang90/include_commit

raft: include commitIndex in heartbeat
*: add rafthttp pkg into test list
Merge pull request #1738 from yichengq/231

*: add rafthttp pkg into test list
rafthttp: send takes raft message instead of bytes

This gives streaming mechanism the chance to assemble and disassemble
raft messages.