Tutorial: fix module name in section 2

snippet -> snippets (to match section 1).

docs/tutorial/2-requests-and-responses.md

@@ -113,7 +113,7 @@ Now update the `urls.py` file slightly, to append a set of `format_suffix_patter
     from django.conf.urls import patterns, url
     from rest_framework.urlpatterns import format_suffix_patterns
 
-    urlpatterns = patterns('snippet.views',
+    urlpatterns = patterns('snippets.views',
         url(r'^snippets/$', 'snippet_list'),
         url(r'^snippets/(?P<pk>[0-9]+)$', 'snippet_detail')
     )