use "-" as redis and mysql weight spliter
add unix protocol support for redis.source
improve hlist performance: remove Head struct
add minheap for channel expired
Merge branch 'master' of github.com:Terry-Mao/gopush-cluster into ketama

Conflicts:
	message/mysql.go
	message/redis.go
Merge branch 'ketama' of github.com:Terry-Mao/gopush-cluster into ketama
update document