Update discovery documentation

Author: sagikazarmark

docs/discovery.md

@@ -6,8 +6,8 @@ The discovery service is a set of static classes which allows to find and use in
 Currently available discovery services:
 
 - HTTP Adapter Discovery
-- PSR Message Discovery
-- PSR URI Discovery
+- PSR-7 Message Discovery
+- PSR-7 URI Discovery
 
 
 ## General
@@ -33,14 +33,13 @@ A start value can be defined for the `classes` property in the following structu
 
 ``` php
 [
-    'name' => [
+    [
         'class'     => 'MyClass',
         'condition' => 'MyCondition',
     ],
 ]
 ```
 
-- `name`: A unique name for the resource, can be overwritten using `register`
 - `class`: The class that is instantiated. There MUST NOT be any constructor arguments.
 - `condition`: The condition that is evaluated to boolean to decide whether the resource is available. The following types are allowed:
     - string: Checked for class existence
@@ -51,9 +50,11 @@ A start value can be defined for the `classes` property in the following structu
 By declaring a start value for `classes` only string conditions are allowed, however the `register` method allows any type of arguments:
 
 ``` php
-MyDiscovery::register('name', 'MyClass', true);
+MyDiscovery::register('MyClass', true);
 ```
 
+Classes registered manually are put on top of the list.
+
 The condition can also be omitted. In that case the class is used as the condition (to check for existence).
 
 The last thing to do is to find the first available resource:
@@ -91,3 +92,66 @@ class MyClass
     }
 }
 ```
+
+
+## Message Factory Discovery
+
+This type of discovery finds installed [PSR-7](http://www.php-fig.org/psr/psr-7/) Message implementations and their factories.
+
+Currently available factories:
+
+- [Guzzle](https://github.com/guzzle/psr7) factory
+- [Diactoros](https://github.com/zendframework/zend-diactoros) factory
+
+
+``` php
+use Http\Message\MessageFactory;
+use Http\Discovery\MessageFactoryDiscovery;
+
+class MyClass
+{
+    /**
+     * @var MessageFactory
+     */
+    protected $messageFactory;
+
+    /**
+     * @param MessageFactory $messageFactory
+     */
+    public function __construct(MessageFactory $messageFactory)
+    {
+        $this->messageFactory = $messageFactory ?: MessageFactoryDiscovery::find();
+    }
+}
+```
+
+## URI Factory Discovery
+
+This type of discovery finds installed [PSR-7](http://www.php-fig.org/psr/psr-7/) URI implementations and their factories.
+
+Currently available factories:
+
+- [Guzzle](https://github.com/guzzle/psr7) factory
+- [Diactoros](https://github.com/zendframework/zend-diactoros) factory
+
+
+``` php
+use Http\Message\UriFactory;
+use Http\Discovery\UriFactoryDiscovery;
+
+class MyClass
+{
+    /**
+     * @var UriFactory
+     */
+    protected $uriFactory;
+
+    /**
+     * @param UriFactory $uriFactory
+     */
+    public function __construct(UriFactory $uriFactory)
+    {
+        $this->uriFactory = $uriFactory ?: UriFactoryDiscovery::find();
+    }
+}
+```