oldestLivingFather.js - now in 50% fewer lines

Lo-dash is awesome! So much more concise now, thanks for the tips.

1. I nested a few lo-dash methods to get more concise, perhaps at the
expense of some readability. How do you decide where to stop to keep
things readable?

2. I used _.pluck and _.max as you suggested, but I didn't do a sort
since it seemed unnecessary with _.max. Would there still be any benefit
to sorting if this was a much bigger collection?
Merge pull request #64 from jbkly/master

oldestLivingFather.js - now in 50% fewer lines