restore **origin** theme and not **default** theme.

[Carreau]

Hi,

I found of about seaborn.reset_defaults() , may I suggest a seaborn.reset_origin() ? Which will partialy take into account user matplotlibrc file and user modification ?

I also found that matplotlib.rcParams.update(matplotlib.rcParamsOrig) is not reliable and that you should make a copy of default param before importing seaborn.

If you are not against and I find some time I could make a PR.

[mwaskom]

Certainly not against it -- it's mostly an artifact of the fact that seaborn was only originally intended to be my own way of managing matplotlib style in a sane way, so I didn't do the best job of making the style framework easy for people to tweak to their own liking. But that's definitely something I'd like to have work better.