make post permalink compatible with old site

Author: gasparnagy

_config.yml

@@ -32,6 +32,14 @@ theme: minima
 plugins:
   - jekyll-feed
 
+permalink: pretty
+defaults:
+  - scope:
+      path: ""
+      type: "posts"
+    values:
+      permalink: /:categories/:year/:month/:title/
+
 # Exclude from processing.
 # The following items will not be processed, by default.
 # Any item listed under the `exclude:` key here will be automatically added to