Vagrantfile: Add 'tree' to installed packages
Vagrantfile: Add 'tree' to installed packages

This package is required by the tutorial notebooks.

JaviMerino/lisa,arnoldlu/lisa,mdigiorgio/lisa,joelagnel/lisa,mdigiorgio/lisa,credp/lisa,ARM-software/lisa,bjackman/lisa,arnoldlu/lisa,credp/lisa,bjackman/lisa,ARM-software/lisa,ARM-software/lisa,joelagnel/lisa,ARM-software/lisa,credp/lisa,credp/lisa