Output for small decimal numbers is misleading
I think that [this](http://stackoverflow.com/questions/12417129/how-do-i-convert-a-column-from-a-pandas-dataframe-from-str-scientific-notation) question on stackoverflow sums up the problem fairly concisely.

In a nutshell, the `0` and `-0` output for very small decimal numbers is misleading and looks a lot like an error.  It might be better just to show scientific notation directly.
