Update pandas version in swan notebook

Dear Zhen,

You will need to add your CERNBox directory as PYTHONPATH:
export PYTHONPATH=$CERNBOX_HOME/.local/lib/python3.5/site-packages:$PYTHONPATH

Please, follow the instructions provided at https://github.com/swan-cern/help/blob/master/advanced/install_packages.md

Regards,
Enrico