Print latest version of packages on conflicts

[bergmark]

Right now:

--  Failure when adding dependencies:
      free: needed (>=4 && <5), but couldn't resolve its dependencies
    needed for package: adjunctions-4.2.1

It would be nice to add the latest version to save me from having too find that elsewhere, perhaps like this:

--  Failure when adding dependencies:
      free: needed (>=4 && <5), latest 4.12.1, but couldn't resolve its dependencies
    needed for package: adjunctions-4.2.1

Using the latest version is often what you want.

[snoyberg]

The code for this was already present, the latest version was simply only being displayed when a dependency was missing, so this was pretty easy. New output sample:

$ stack build --dry-run
While constructing the BuildPlan the following exceptions were encountered:

--  Failure when adding dependencies:
      Cabal: needed (<1.1), latest is 1.22.4.0, but 1.18.1.5 found
    needed for package: stack-0.1.1.0

Can you test out master?

[bergmark]

👍 Thanks!