Update index.md
Update index.md

I think that "comprehensive" sounds much more positive than "exhaustive."
ubuntuvim/guides,skaterdav85/guides,jkarsrud/guides,ubuntuvim/guides,knownasilya/guides,jkarsrud/guides,davidpett/guides,MarkMT/guides,HeroicEric/guides,nicobot/guides,bmac/guides,skaterdav85/guides,bmac/guides,jkarsrud/guides,davidpett/guides,knownasilya/guides,boztek/guides,boztek/guides,tleskin/guides,nicobot/guides,tleskin/guides,knownasilya/guides,bmac/guides,MarkMT/guides,skaterdav85/guides,nicobot/guides,bmac/guides,ubuntuvim/guides,jkarsrud/guides,davidpett/guides,tleskin/guides,ubuntuvim/guides,vikram7/guides,HeroicEric/guides,boztek/guides,HeroicEric/guides,vikram7/guides,skaterdav85/guides,davidpett/guides,knownasilya/guides,MarkMT/guides,MarkMT/guides,vikram7/guides