Connection pool feature.

[bearnard]

It would be quite useful to have a connection pooling mechanism.

I'm not sure if we should perhaps look at porting node-pool or something similar.

[kengonakajima]

I think so too. I saw node-pool(generic-pool) and found it's really small/simple and easy to port to Lua. I also found it's truly generic so we don't have to implement it with luvit-mysql. My next luvit-redis, could also be combined with it.