v5.1-3

Major changes

• Roxygen documentation improvements.

Minor changes and bug fixes

• zquantile with Amelia imputed data now working. #277

• vcov now works with rq quantile regression models.

• More informative error handling for conflicting timeseries model
  arguments. #283

• Resolved and issue with relogit that produced a warning when the fitted
  model object was passed to predict. #291