Add logging to Gitpan::Github

For #15
Fix Gitpan::Github to work with CanDistLog.

BUILD methods are supposed to stack with inheritance, but Moo isn't
stacking roles in.  So Gitpan::Github->new does not run
Gitpan::Role::CanDistLog->BUILD.  To remedy this, Gitpan::Github
wraps its BUILD around CanDistLog's.

And now the Github repo name is required so CanDistLog can build
the dist logging directory.

For #15