[[!comment format=mdwn
 username="joey"
 subject="""comment 3"""
 date="2016-02-10T16:09:08Z"
 content="""
Would probably be better to use `before`, since `combineProperties`
needs a description of the combined properties.

Using `doNothing` is kind of a hack, it would make propellor say it was
running "noop property". Perhaps better to use a SemiGroup than a Monoid.
"""]]
