temp commit
merge
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/nc_stats.c
1.add a new distribution method named 'modhash', which divid the hash by mod%420000, and each hash key map to a backends.
config file should give the hash keys segment to assign each backend's key segment.
2.add support of 'getkey SP_NAME hash_key_mod_number' to get the correspond backend config
3.add support of get server config by twemproxy stat port. e.g. get the servers list: 'get SP_NAME servers'
4.add server function has do some job,but not finished yet, we'll restart it later.