clarify quick start in readme.txt
clarify quick start in readme.txt

badlogic/avian,badlogic/avian,lostdj/avian,bigfatbrowncat/avian-pack.avian,MaartenR/avian,getlantern/avian,lwahlmeier/avian,joshuawarner32/avian,MaartenR/avian,getlantern/avian,minor-jason/avian,ucdseniordesign/avian,bgould/avian,joshuawarner32/avian,bigfatbrowncat/avian-pack.avian,marcinolawski/avian,bgould/avian,bgould/avian,minor-jason/avian,ucdseniordesign/avian,dicej/avian,getlantern/avian,dicej/avian,bigfatbrowncat/avian-pack.avian,lwahlmeier/avian,lostdj/avian,dicej/avian,lostdj/avian,bgould/avian,marcinolawski/avian,lwahlmeier/avian,badlogic/avian,minor-jason/avian,joshuawarner32/avian,ucdseniordesign/avian,joshuawarner32/avian,lostdj/avian,minor-jason/avian,dicej/avian,getlantern/avian,marcinolawski/avian,MaartenR/avian,marcinolawski/avian,badlogic/avian,MaartenR/avian,bigfatbrowncat/avian-pack.avian,ucdseniordesign/avian,lwahlmeier/avian