Add timeout to Redis request when the Redis server stops responding

Hello @nicks, @don-neufeld:

Please review the following commits I made in branch 'xiao-add-redis-request-timeout'.

efe4ae4259e3f5ed694f362945e5176d57af849f (2013-09-03 17:23:31 -0700)
Add timeout to Redis request when the Redis server stops responding


R=@nicks
R=@don-newfeld