Option to use pooled connections in `mysql` driver

[jcrugzz]

The complexity of this might be a little hairy but it would be sweet if you could use connection pooling underneath the hood by passing in an option.

The reason I mention this is for projected performance gains. @brianloveswords thoughts?

[brianloveswords]

I'd definitely be into adding it as a mysql specific driver option! I'll play around and see what I can come up with.