nginx: fix broken bbb-playback location

closes #71

mod/nginx/bbb/presentation.nginx

@@ -15,9 +15,11 @@
 # You should have received a copy of the GNU Lesser General Public License along
 # with BigBlueButton; if not, see <http://www.gnu.org/licenses/>.
 #
-
-        location /playback/presentation {
-                alias /www/presentation;
+        location /playback/presentation/2.0/playback.html {
+                return 301 /playback/presentation/2.3/$arg_meetingId?$query_string;
+        }
+        location /playback/presentation/2.3 {
+                try_files $uri /playback/presentation/2.3/index.html;
         }
 
         location /presentation {

mod/nginx/bigbluebutton

@@ -22,6 +22,7 @@ server {
   server_name _;
   access_log /dev/stdout;
   absolute_redirect off;
+  root /www/;
   
   # redirect to greenlight
   location = / {