WIP: Tutorial example files

I'd like to ship a few small example ROOT files and use them in the tutorial (and for bug reports / tests). At the moment there's these three files with about 1 MB total:
```
 19K  test_file.root
405K  hsimple.root
202K toy_sigbkg.root
```
The first one I took from the rootpy repo, the other two from the ROOT repo.

@pwaller Do you think these are OK? Do you have better example files?