Fix typo

guidelines/hierarchy.md

@@ -39,7 +39,7 @@ Guidelines
 
 ### Root (README et al.) ###
 
-It's good to keep as little files here as possible, but few names are
+It's good to keep as little files here as possible, but few names have
 already become de-facto standard.
 
 Every decent project has a *README* file in the root folder.  You can name