BUG: plotting grouped_hist with a single row frame #10214
Should closes https://github.com/pydata/pandas/issues/10214

We had a couple stray commits slip in. Will cleanup later.
 @scls19fr can you rebase on master. ping when green.
 Sorry @jreback I don't feel very confortable with Git.

I did:

```
$ git rebase master

$ git pull

$ git push
```

What should I do ?

I would like to have my master branch sync with upstream.
 Maybe this PR https://github.com/pydata/pandas/pull/10298 is better.
I deleted my repository. Fork again master. Create branch. Change 3 files and send PR.
