Rename development branch to 0.2.x

Author: SimonFrings

README.md

@@ -4,6 +4,11 @@
 
 [ReactPHP](https://reactphp.org/)'s filesystem component that enables non-blocking filesystem operations.
 
+> **Development version:** This branch contains the code for the upcoming 0.2
+> release which will be the way forward for this package.
+>
+> See [installation instructions](#install) for more details.
+
 **Table of Contents**
 
 * [Quickstart example](#quickstart-example)
@@ -262,7 +267,7 @@ This project follows [SemVer](https://semver.org/).
 This will install the latest supported version:
 
 ```bash
-$ composer require react/filesystem:^0.2
+$ composer require react/filesystem:^0.2@dev
 ```
 
 Installing any of the event loop extensions is suggested, but entirely optional.