Added new file lib/Twitter/List.pm

diff --git a/bin/app-example.pl b/bin/app-example.pl
- Readability cleanup

diff --git a/lib/Twitter/List/CPANAuthors.pm b/lib/Twitter/List/CPANAuthors.pm
- Making use of new base package Twitter::List for create_list() and
  populate_list() functions
- Removed Data::Dumper
- Removed package var $dbg (now controlled by Twitter::List)
- Migrated several list creation functions to Twitter::List