Version 1.3

Changes:

• pencil sounds split into "pencil_erase" & "pencil_write" groups
• fixed arithmetic operations on SoundGroup
• renamed node sound files
• SoundGroup:play returns handle or nil only
• using built-in type function on SoundGroup instance will return "SoundGroup"
• added sounds:
  • bee
  • bees
  • bumble_bee
  • chicken
  • clock_tick
  • coyote_howl
  • crow_caw
  • duck_quack
  • goat_bleat
  • grasshopper
  • hyena
  • jaguar_saw
  • lion
  • mouse
  • owl
  • peacock
  • piano
  • pigeon
  • tiger_roar
  • tiger_snarl
  • undead_moan
  • vulture
  • watch_tick
  • whistle
  • wolf
  • yak
  • zebra
  • zipper