Warn if new version is available

[PeterAustinMoore]

New versions often get buried in the communications and don't always reach the masses. A version check and dialog if the version is not new (and being run in gui-mode) or a warning if being run headlessly would be ensure this communication.

[shua123]

Is this not already implemented? There has been previous discussion on the pros and cons of notification. https://github.com/socrata/datasync/issues/78

[levyj]

I also thought this already existed, at least for the GUI.

What would the warning in headless mode mean? On one hand, one does not want to miss it for automated jobs. On the other hand, it cannot halt completion of the job unless there is a way to bypass. There will be situations where a user wants to use an older version intentionally.

What did ever happen with #78? It looks as if it was closed, even though the intent was to address it in a later version.