explorer plot should scale appropriately to fit data

[jtyberg]

The explorer widget should scale to the data that it plots.

Contrast the df.plot() output, which produces the data scaled to the viewing area with the explore(df) plot, which forces the user to scroll:

[peller]

I think the problem is that your timestamps are being treated as ordinals. Right now, you need to convert the column to a Date type in your dataframe in the kernel -- see the fourth code cell in this example Try that and see if it gives you the behavior you want. We clearly need a friendlier way to recognize and coerce the data type.

[peller]

@lbustelo: we could try introducing heuristics to identify and convert dates. It might make more sense to do that in urth-core-dataframe than on the client e.g. urth-viz-explorer. Thoughts?