Issue with dates

[tgriesser]

It doesn't look like there is any handling for properly formatting dates on insert, which is triggering an "Incorrect datetime value" error.

It looks like there should be something similar to https://github.com/felixge/node-mysql/blob/7534b99bd0b9b57309abb6480b1549fe5ef93e74/lib/protocol/SqlString.js#L82 this method in order to format things properly.

I can open a PR, just wanted to confirm first that you're not looking to put this on the user to handle the formatting.

[mscdex]

Pull requests are welcome :-)