Make LoggerGroup `loggers` argument use the add_loggers method
Make LoggerGroup `loggers` argument use the add_loggers method

Simplifies the API IMHO.

Signed-off-by: Armin Ronacher <51e1b983df8328b92ad653ca9129d9a11178303a@active-4.com>

redtoad/logbook,redtoad/logbook,dvarrazzo/logbook,Rafiot/logbook,alonho/logbook,mbr/logbook,Rafiot/logbook,alonho/logbook,mitsuhiko/logbook,dvarrazzo/logbook,maykinmedia/logbook,maykinmedia/logbook,fayazkhan/logbook,DasIch/logbook,DasIch/logbook,omergertel/logbook,pombredanne/logbook,fayazkhan/logbook,mbr/logbook,omergertel/logbook,alex/logbook,alex/logbook,RazerM/logbook,dommert/logbook,narfdotpl/logbook,DasIch/logbook,alonho/logbook,FintanH/logbook,Rafiot/logbook,omergertel/logbook