missing 's' in nginx-vhost(s)

sudo rm -r /var/lib/dokku/plugins/nginx-vhost
rm: cannot remove ‘/var/lib/dokku/plugins/nginx-vhost’: No such file or directory
rename nginx-vhosts instead of deleting. update readme
rm backup if we find ourselves with another nginx-vhosts copy
Updated install to use existing plugin's install routines.
Updated install instructions to reflect new install script.
Merge branch 'master' of github.com:mikexstudios/dokku-nginx-alt