Update readme to require users use 0.1 instead of dev-master

Author: n7studios

README.md

@@ -1,23 +1,26 @@
 # ConvertKit SDK PHP
+
 ConvertKit's official PHP SDK
 
 ### Installation
 
-#### Standard installation
+#### Standard Installation
 
 1. Download or clone this repository
 2. Run `composer install`
 3. Add `./vendor/autoload.php` to your project
 
-#### Installation with package manager
+#### Installation with Package Manager
 
 If your project uses [Composer](https://getcomposer.org/), you can install the ConvertKitSDK-PHP package as a composer package. This allows you to have this project as a dependency without the ConvertKitSDK-PHP files being checked into your source code.
 
 ```shell
-composer require convertkit/convertkitapi:dev-master
+composer require convertkit/convertkitapi:0.1
 ```
 
-Please note that since ConvertKitSDK-PHP is not yet versioned, your project will always download the latest files from master every time you run `composer install` which may subject you to breaking changes in the future.
+**If you previously use or rely on `dev-master`, please use the `0.1` release to maintain compatibility with no breaking changes.**
+
+This package is now versioned, and `1.0` will introduce breaking changes to bring this package up to date with coding standards, PHP versions and third party library versions.
 
 ### Usage