MySQL Close cursor and connection on commit

[felipehertzer]

Hi @josephmancuso,

I'm having issues with lots of timeouts/open connections, where it seems like the connection isn't being closed.

I was checking MySQLConnection, and I saw that it never closes the cursor, I believe it could cause a memory leak.

I also identified that if I use transactions it will never close the connection, because the code is checking to close the connection in the query function and not in the commit function. Example:

DB.begin_transaction()
QueryBuilder().table('user').update('status', 1)
DB.commit()

This is pull request is an idea, I'm happy to discuss any solution.

Thanks.