Work towards #56: Splitting up the README

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

async-method-invocation/index.md

@@ -0,0 +1,26 @@
+---
+layout: pattern
+title: Async Method Invocation
+folder: async-method-invocation
+categories: pattern_cat
+tags: pattern_tag
+---
+
+**Intent:** Asynchronous method invocation is pattern where the calling thread
+is not blocked while waiting results of tasks. The pattern provides parallel
+processing of multiple independent tasks and retrieving the results via
+callbacks or waiting until everything is done. 
+
+![alt text](./etc/async-method-invocation.png "Async Method Invocation")
+
+**Applicability:** Use async method invocation pattern when
+
+* you have multiple independent tasks that can run in parallel
+* you need to improve the performance of a group of sequential tasks
+* you have limited amount of processing capacity or long running tasks and the
+  caller should not wait the tasks to be ready
+
+**Real world examples:**
+
+* [FutureTask](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/FutureTask.html), [CompletableFuture](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html) and [ExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorService.html) (Java)
+* [Task-based Asynchronous Pattern](https://msdn.microsoft.com/en-us/library/hh873175.aspx) (.NET)