Use consistent folder naming structure
Use consistent folder naming structure

Most of the references to the folder structure on the tutorial do not contain the leading slash. 
This removes leading slashes in the `Installing Addons` guide to match the rest of the Guides.
skaterdav85/guides,HeroicEric/guides,skaterdav85/guides,davidpett/guides,knownasilya/guides,MarkMT/guides,davidpett/guides,davidpett/guides,HeroicEric/guides,MarkMT/guides,MarkMT/guides,nicobot/guides,jkarsrud/guides,knownasilya/guides,jkarsrud/guides,tleskin/guides,jkarsrud/guides,knownasilya/guides,jkarsrud/guides,tleskin/guides,skaterdav85/guides,tleskin/guides,nicobot/guides,knownasilya/guides,MarkMT/guides,HeroicEric/guides,nicobot/guides,davidpett/guides,skaterdav85/guides