Update README.md

Author: Holt59

README.md

@@ -12,10 +12,21 @@ How to... ?
 
 **Installation**
 
+If you want the latest version of the plugin (currently **Boostrap 3**):
 ```
 composer require holt59/cakephp3-bootstrap-helpers:dev-master
 ```
 
+If you want the latest **Bootstrap 3** version of the plugin:
+```
+composer require holt59/cakephp3-bootstrap-helpers:3.*
+```
+
+If you want to test the **Bootstrap 4** version of the plugin (alpha):
+```
+composer require holt59/cakephp3-bootstrap-helpers:bootstrap4-alpha
+```
+
 **Documentation**
 
 The full plugin documentation is available at https://holt59.github.io/cakephp3-bootstrap-helpers/.