Improve pool documentation.
Improve pool documentation.

Charlesdong/redigo,stvp/redigo,garyburd/redigo,shosti/redigo,linkeo/redigo,outrightmental/go-redigo,mbrukman/redigo,gomodule/redigo,blackbeans/flume-bridge,brodock/redigo,kylebrandt/redigo,iron-s/redigo,cloudnautique/redigo,beni55/redigo,ninjasphere/redigo,kpumuk/redigo,lvtiendev/redigo,MCProHosting/redigo,zhgo/redis,blackbeans/flume-bridge,Wang/redigo,nativetouch/redigo