Add transaction blocks

This adds transaction queue functionality to the SQLConnectionHandler. There is the ability to have multiple queues per connection handler, as well as the ability to use returned values from a previous sql query in subsequent queries in the queue.
Queues are created using the `create_queue` method and then added to using the `add_to_queue` method. Calling `execute_queue` executes the queue, as expected.
To use previous result values, you need to know the order a previous query returns in. Then, you can use a similar format to the string format function to insert these values. The tests added give a good example of this functionality.
Can you describe this data structure a little bit?  I think it's a dict of `{str: list}` where the key is the name of the queue and the list is a list of 2-tuples of `(sql, args)` where `args` is itself a tuple (or list).  But it would be nice to have it explicitly described, perhaps in the class's docstring?