beef up m.deferred docs

docs/mithril.deferred.md

@@ -8,6 +8,12 @@ The deferred object can then *apply* a value by calling either `resolve` or `rej
 
 Each computation function takes a value as a parameter and is expected to return another value, which in turns is forwarded along to the next computation function (or functions) in the tree.
 
+The deferred object returned by `m.deferred` has two methods: `resolve` and `reject`, and one property called `promise`. The methods can be called to dispatch a value to the promise tree. The `promise` property is the root of the promise tree. It has a method `then` which takes a `successCallback` and a `errorCallback` callbacks. Calling the `then` method attaches the computations represented by `successCallback` and `errorCallback` to the promise, which will be called when either `resolve` or `reject` is called. The `then` method returns a child promise, which, itself, can have more child promises, recursively.
+
+The `promise` object is actually a function - specifically, it's an [`m.prop`](mithril.prop.md) getter-setter, which gets populated with the value returned by  `successCallback` or `errorCallback` (depending on whether `resolve` or `reject` got called).
+
+Note that Mithril promises are not automatically integrated to its automatic redrawing system. If you wish to use third party asynchronous libraries (for example, `jQuery.ajax`), you should also consider using [`m.startComputation` / `m.endComputation`](mithril.computation.md) if you want views to redraw after requests complete.
+
 ---
 
 ### Usage
@@ -27,6 +33,48 @@ greetAsync()
 	.then(function(value) {console.log(value)}); //logs "hello world" after 1 second
 ```
 
+#### Retrieving a value via the getter-setter API
+
+```javascript
+//asynchronous service
+var greetAsync = function() {
+	var deferred = m.deferred();
+	setTimeout(function() {
+		deferred.resolve("hello");
+	}, 1000);
+	return deferred.promise;
+};
+
+//asynchronous consumer
+var greeting = greetAsync()
+var processed = greeting.then(function(value) {return value + " world"})
+
+console.log(greeting()) // undefined - because `deferred.resolve` has not been called yet
+
+setTimeout(function() {
+	//now `deferred.resolve` has been called
+	console.log(greeting()) // "hello"
+	console.log(processed()) // "hello world"
+}, 2000)
+```
+
+#### Integrating to the Mithril redrawing system
+
+```javascript
+//asynchronous service
+var greetAsync = function() {
+	m.startComputation();
+	
+	var deferred = m.deferred();
+	setTimeout(function() {
+		deferred.resolve("hello");
+		
+		m.endComputation();
+	}, 1000);
+	return deferred.promise;
+};
+```
+
 ---
 
 ### Differences from Promises/A+