Work towards #56: Splitting up the README

I did the job and splitted up the readme, hopefully everything was
splitted correctly...

strategy/index.md

@@ -0,0 +1,20 @@
+---
+layout: pattern
+title: Strategy
+folder: strategy
+categories: pattern_cat
+tags: pattern_tag
+---
+
+**Intent:** Define a family of algorithms, encapsulate each one, and make them
+interchangeable. Strategy lets the algorithm vary independently from clients
+that use it.
+
+![alt text](./etc/strategy_1.png "Strategy")
+
+**Applicability:** Use the Strategy pattern when
+
+* many related classes differ only in their behavior. Strategies provide a way to configure a class either one of many behaviors
+* you need different variants of an algorithm. for example, you might define algorithms reflecting different space/time trade-offs. Strategies can be used when these variants are implemented as a class hierarchy of algorithms
+* an algorithm uses data that clients shouldn't know about. Use the Strategy pattern to avoid exposing complex, algorithm-specific data structures
+* a class defines many behaviors, and these appear as multiple conditional statements in its operations. Instead of many conditionals, move related conditional branches into their own Strategy class