Migrate docs.scipy.org

[tupui]

The content of docs.scipy.org should be migrated here.

xref scipy/docs.scipy.org#59

[tupui]

Once SciPy's PR is in, we can deprecate or remove the page.

[lucascolley]

I think we should point https://docs.scipy.org to https://docs.scipy.org/doc/scipy/ now. And having the URL be https://scipy.org/doc or https://scipy.org/docs seems better to me.