Added a note about getting a 301 when using httpie and forgetting to add a trailing slash to a url

docs/tutorial/1-serialization.md

@@ -331,7 +331,7 @@ You can install httpie using pip:
 
     pip install httpie
 
-Finally, we can get a list of all of the snippets:
+Finally, we can get a list of all of the snippets (note the trailing / on the snippets/ url below. If you don't include it you may get a confusing '301 Moved Permanently' response because Django's default behavior is to redirect to a url with a trailing /):
 
     http http://127.0.0.1:8000/snippets/