Fix outdated checks

This PR fixes #1141. Previously the API server would return results "in order". I made a terrible assumption that this was a good idea. This will now guarantee that we only get the newest version that satisfies the constraint.

Additionally, this PR changes the information given back to the user. Instead of just displaying the newer version, this will now account for multiple updates being available (at different sources) and tell the user which version they are upgrading from:

```text
The following cookbooks have newer versions:
  * nginx (1.8.0 => 2.6.2)
  * nginx (1.8.0 => 3.0.0) [https://berkshelf.sethvargo.com]
```