Add conflict resolution instructions to staging.yaml

@NoahCarnahan @emord @twymer based on what we just talked about.  Lemme know if this isn't clear, or feel free to push clarifications to this PR.
i would do:
```
$ git checkout master
$ git pull origin master
$ git checkout foo
$ git rebase master
$ git push -f origin foo
```

but that might be a matter of preference.