Improve documentation for `min` and `max`

* Remove ambiguous wording "If iterator is passed" since iterator
  functions are often predicates that pass or fail
* Make examples given for `min` and `max` more consistent with each
  other
* Remove other occurences of similar ambiguous wording in documentation

I had not noticed the documentation for the `max` function, which would have clarified things.  I had clicked on the `min` link in the left nav, which scolled past the `max` documentation.  Other people, who are trying to quickly reference the docs, would probably have the same issue.