Add example of using multiple queries in a single statement to documentation

[henriksjostrom]

No description provided.

[Sannis]

You can look at the tests for synchronous example: https://github.com/Sannis/node-mysql-libmysqlclient/blob/master/tests/low-level-sync/test-class-mysqlconnection-sync.js#L51-L85

Are you really need async version for this?

[SLM-Linus]

I would really need an async version of this, is it enough to replace the sync in the function names and add an callback with (err, res) parameters?

[henriksjostrom]

Yes, async would be very useful for me.