Added ggrep detection for OSX

AAXtoMP3

@@ -5,6 +5,7 @@ set -o errexit -o noclobber -o nounset -o pipefail
 codec=libmp3lame
 extension=mp3
 mode=chaptered
+grep=$(grep --version | grep -q GNU && echo "grep" || echo "ggrep")
 
 if [ "$#" -eq 0 ]; then
         echo "Usage: bash AAXtoMP3.sh [--flac] [--single] AUTHCODE {FILES}"