Work on #213

- properly categorize all patterns
- remove pattern list from readme
- minor fixes to readme
- removed "introduction" because its not a pattern and an error i
committed some time ago

callback/index.md

@@ -3,8 +3,8 @@ layout: pattern
 title: Callback
 folder: callback
 permalink: /patterns/callback/
-categories: pattern_cat
-tags: pattern_tag
+categories: Other
+tags: Java
 ---
 
 **Intent:** Callback is a piece of executable code that is passed as an