I think it might be better to always ask people to specify `hadoop.version` and then just explain that in some cases they need to add a profile to work around problems in the hadoop dependency graph. Otherwise sometimes we are relying on the profile to set `hadoop.version` and it could be a bit confusing to users what is going on.

```
mvn -Pyarn -Dhadoop.version=2.2.X -Phadoop-2.2  -DskipTests clean package
```

The header here says "Apache Hadoop 2.2.X" but the actual example can't be directly generalized to 2.2.X without them digging around the build more.