reprs no longer return anything in the notebook
In https://github.com/pandas-dev/pandas/pull/14904 I added an `NDFrame._ipython_display_`, which handles publishing what the user has configured (html, table schema, latex, text).

An unintended consequence of that, is that our DataFrame and Series reprs invoked by the notebook no longer return anything, so there's no `Out[x]` and nothing is stored in the `Out` dictionary. [Here's a comparison notebook](http://nbviewer.jupyter.org/gist/TomAugspurger/6aee20f69aafdb70ae65ebef77bb12f0).

cc @rgbkrk

For the jupyter folks (maybe @Carreau if you have time), is there any way around this? Does using `_ipython_display_` mean you can't have a "real output" from a cell?