037: Map.mapValues is a view

Show mapValues alongside map for contrast.

Maybe this doesn't reveal too much.

And maybe mapValiews isn't too groan-worthy.

Brevity is the soul of nits
Merge pull request #78 from som-snytt/puzzle/view-to-a-shill-squash

Proposing a new puzzler: 'A View to a Shill'