added ability to use show commands on objects that are not the current p...

...lot

@bryevdv @LilaHickey @kdodia 

added a function so we could show crossfilter in the notebook (and debug why the css is not looking great)


LGTM too. In example:`examples/glyphs/glyph.ipynb` we could then do:
![screen shot 2014-07-15 at 6 25 16 pm](https://cloud.githubusercontent.com/assets/4940549/3592781/7f6a247e-0c77-11e4-9332-0e27f665feb5.png)

Instead of
![screen shot 2014-07-15 at 6 25 01 pm](https://cloud.githubusercontent.com/assets/4940549/3592782/8505bd58-0c77-11e4-8ec0-c60bd949e581.png)