Work towards #56: Add permalink to every pattern

This makes cleaner URLs thanks to jekyll

abstract-factory/index.md

@@ -2,6 +2,7 @@
 layout: pattern
 title: Abstract Factory
 folder: abstract-factory
+permalink: /patterns/abstract-factory/
 categories:
  - pattern_cat
  - creational
@@ -22,4 +23,4 @@ objects without specifying their concrete classes.
 
 **Real world examples:**
 
-* [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
+* [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)