Request change to boxplot code to handle tiny data sets better

[dicook]

In situations when we want to make side-by-side boxplots, ideally if there are less than 5 points that group is shown as dots.

Here is the current behaviour:

and this is the desirable behaviour:

Notice the samples at NT and ACT only have 3 and 2 points respectively, so showing them as boxplots is misleading.

A diff of the code change is at:

dicook@7dbc03e

[teunbrand]

I have similar objections to boxplots too (i.e. what is the point of a 5-number summary of a group of 3 members?). For backwards compatibility though, I'd suggest to add a argument like min_group = 1 that somebody can set to 5 if they'd want to activate this behaviour.