Improve Message Factory documentation

Author: sagikazarmark

docs/components/message-factory.md

@@ -6,8 +6,9 @@
 ## Rationale
 
 While it should be possible to use every PSR-7 aware HTTP client with any RequestInterface implementation,
-creating the request objects will still tie an application to a specific implementation.
-In the case of reusable libraries, an application could end up installing several request implementations.
+creating the request objects will still tie the code to a specific implementation.
+If each reusable library is tied to a specific message implementation,
+an application could end up installing several message implementations.
 The factories abstract away from this.
 
 The FIG was pretty straightforward by NOT putting any construction logic into PSR-7.
@@ -23,22 +24,3 @@ This package provides interfaces for PSR-7 factories including:
 - `StreamFactory`
 - `UploadedFileFactory` - WIP (PRs welcome)
 - `UriFactory`
-
-
-A [virtual package](/httplug/virtual-package) ([php-http/message-factory-implementation](https://packagist.org/providers/php-http/message-factory-implementation))
-MAY be introduced which MUST be versioned together with this package.
-
-The adapter repositories provide wrapper classes for those factories to
-implement the `Http\Message\MessageFactory` interface.
-
-
-### General usage
-
-``` php
-use Http\Message\SomeFactory;
-
-class MyFactory implements SomeFactory
-{
-
-}
-```