perl6_family_completion.sh

Perl6 tab-completion now has its own repository, so
perl6_family_completion.sh now links to it.
(tabcomp-p6/perl6_family_completion.sh)
Please clone from https://github.com/firefish5000/tabcomp-p6.git if all
you want is perl6 tab-completion. (this repo contains it as a subtree)