Add a modified describe

[AshlinHarris]

I have used something like this in several projects:

function fully_describe(DF)
	q = describe(DF)
	q.num_unique_vals = map(x->length(DF[!,x] |> unique), names(DF))
	show(q, allrows=true, allcols=true) 
end

Are there any other summary statistics that are useful for understanding DataFrames?