Origin of spacy.matcher attributes

Make it clear that Matcher attributes live in spacy.matcher.attrs.

website/docs/usage/rule-based-matching.jade

@@ -18,7 +18,9 @@ p Here's a minimal example. We first add a pattern that specifies three tokens:
 
 p
     |  Once we've added the pattern, we can use the #[code matcher] as a
-    |  callable, to receive a list of #[code (ent_id, start, end)] tuples:
+    |  callable, to receive a list of #[code (ent_id, start, end)] tuples.
+    |  Note that #[code LOWER] and #[code IS_PUNCT] are data attributes
+    |  of #[code Matcher.attrs].
 
 +code.
     from spacy.matcher import Matcher