[1.8.x] Used relative models imports in the GIS tutorial.

Backport of bb7042cda from master.

docs/ref/contrib/gis/tutorial.txt

@@ -470,7 +470,7 @@ with the following code::
 
     import os
     from django.contrib.gis.utils import LayerMapping
-    from models import WorldBorder
+    from .models import WorldBorder
 
     world_mapping = {
         'fips' : 'FIPS',
@@ -738,7 +738,7 @@ Let's dive right in.  Create a file called ``admin.py`` inside the
 ``world`` application with the following code::
 
     from django.contrib.gis import admin
-    from models import WorldBorder
+    from .models import WorldBorder
 
     admin.site.register(WorldBorder, admin.GeoModelAdmin)