init ci, kv works
add leveldb config
command lookup & redis protocal implemented

1. add command lookup
2. redis protocal implemented
3. add -DHAVE_ASSERT_PANIC
4. add leveldb config

    leveldb.compression
    leveldb.read_verify_checksum
    leveldb.write_sync

5. support empty value
6. fix mem leak
rename src/ndb_msg.c -> src/ndb_message.c
format
implement background compact
expire/ttl implemented
log improve

1. add log level & ms in log
2. use log_debug/log_notice/log_warn/log_error
EMFILE bug fix

1. fix EMFILE
2. fix bug on ndb_conn_recv_done