[charms][sunbeam] Proposing Guillaume Boutry for charms-core

Hi All Guillaume has been working on the Sunbeam Charms for the last few months and has proven an able reviewer and contributor to the charms; we need to dis-entangle the sunbeam project charms from the main openstack charms set but until that work is completed I'd like to propose Guillaume as a member of the charms-core team. Cheers James