DOC: Add intersphinx extension and links to some packages.
DOC: Add intersphinx extension and links to some packages.

arokem/seaborn,anntzer/seaborn,petebachant/seaborn,lukauskas/seaborn,phobson/seaborn,sauliusl/seaborn,mwaskom/seaborn,phobson/seaborn,arokem/seaborn,mwaskom/seaborn,anntzer/seaborn,lukauskas/seaborn