preparing for flood test
refactor code

use open_socket() function to unify all socket connect/bind code
use HOST_NAME_MAX
remove find_open_port() and get_host_name()
stick to ipv4 for now
use tpc_connect() and udp_connect() in Client
use udp_bind()
unify TCP and UDP connection
Preparing to separate Buffer and Marshal logic

Buffer: a stream of bytes (TCP/UDP use different kind of Buffer)
Marshal: the way to represent data in Buffer (Serialization spec)
Merge branch 'master' of github.com:santazhang/simple-rpc
move more io code into buffer.h and buffer.cc
add UnboundedBuffer
update hash function for polling fd
rlog: allow setting qps interval