Bumped version 2.4.0

    * Added a useful class called SQLStepQueue
        * Requires MemSQL 2.5 to work due to using JSON under the hood.
        * Fully atomic queue, that is designed to also store data forever
        * Each enqueued item can be started, multiple steps can be executed on it, and then it can be stoped
        * Timing information for each step is stored on the item's execution row