Widont short headlines

I had a problem with a two-word headline overflowing its containing box on a mobile layout, thanks to inadvertent use of widont and the non-breaking space it inserted. Thinking about it, in a case like this, four words is probably the minimum that should have its trailing words non-breaking, but I think there's room for discussion there.

This perhaps isn't the best solution, since I am short-circuiting the regexp, but it was easier to get something that worked and provided a better point for awareness of the problem.