C++11 feature: std::async (#47)

* C++11 feature: std::async

CPP11.md

@@ -45,6 +45,7 @@ C++11 includes the following new library features:
 - [unordered containers](#unordered-containers)
 - [std::make_shared](#stdmake_shared)
 - [memory model](#memory-model)
+- [std::async](#stdasync)
 
 ## C++11 Language Features
 
@@ -738,6 +739,24 @@ C++11 introduces a memory model for C++, which means library support for threadi
 
 See the sections on: [std::thread](#stdthread)
 
+### std::async
+`std::async` runs the given function either asynchronously or lazily-evaluated, then returns a `std::future` which holds the result of that function call.
+
+The first parameter is the policy which can be:
+1. `std::launch::async | std::launch::deferred` It is up to the implementation whether to perform asynchronous execution or lazy evaluation.
+1. `std::launch::async` Run the callable object on a new thread.
+1. `std::launch::deferred` Perform lazy evaluation on the current thread.
+
+```
+int foo() {
+    /* Do something here, then return the result. */
+    return 1000;
+}
+
+auto handle = std::async(std::launch::async, foo);  // create an async task
+auto result = handle.get();  // wait for the result
+```
+
 ## Acknowledgements
 * [cppreference](http://en.cppreference.com/w/cpp) - especially useful for finding examples and documentation of new library features.
 * [C++ Rvalue References Explained](http://thbecker.net/articles/rvalue_references/section_01.html) - a great introduction I used to understand rvalue references, perfect forwarding, and move semantics.