Create some common sense/"sanity" checks for datetime ingest

[jamesrco]

These basic checks could include:

1. Alert for dates apparently far in the past that might have been mis-recognized when using %Y in tryFormats
2. Alert for dates in the future (same issue with tryFormats)
   *** could use the Sys.time() as the refernce point

Others?

[jamesrco]

Both of these would only trigger a warning() (not a stop()) if the test fails; obviously, there are many instances where old/future dates are valid

[jamesrco]

Could set thresholds at < 1980 or > 24 hr from Sys.time