Work towards #56: Add permalink to every pattern

This makes cleaner URLs thanks to jekyll

dependency-injection/index.md

@@ -2,6 +2,7 @@
 layout: pattern
 title: Dependency Injection
 folder: dependency-injection
+permalink: /patterns/dependency-injection/
 categories: pattern_cat
 tags: pattern_tag
 ---
@@ -18,4 +19,4 @@ inversion of control and single responsibility principles.
 **Applicability:** Use the Dependency Injection pattern when
 
 * when you need to remove knowledge of concrete implementation from object
-* to enable unit testing of classes in isolation using mock objects or stubs
+* to enable unit testing of classes in isolation using mock objects or stubs