Correction to Boxplot Documentation Code

This is the Pull request corresponding to Issue #1009.

This fixes the documentation to both check that the outliers are not empty for each category as well as to (if needed) shorten the lengths of the stems (if needed) to the minimums or the maximums.

This does not add an additional example that does not have any outliers.

This corrects every instance of the boxpolot code that I could find.