Update README.md

Author: Holt59

README.md

@@ -3,6 +3,10 @@ CakePHP 3.x Helpers for Bootstrap
 
 CakePHP 3.0 Helpers to generate HTML with @Twitter Boostrap style: `Html`, `Form`, `Modal` and `Paginator` helpers available!
 
+**Important:** From now, this repository will not target a specific bootstrap version, so you may encounter errors if you are requiring `cakephp3-bootstrap3-helpers` instead of `cakephp3-bootstrap-helpers` or loading `Bootstrap3` plugin instead of `Bootstrap`. Do not hesitate to open a new issue if you have trouble getting the plugin working.
+
+**Important:** The current version of bootstrap is v3.3.5, a new `bootstrap4-alpha` branch has been created with the aim of supporting Bootstrap 4. When the final version of Bootstrap 4 will be released, the `bootstrap4-alpha` branch will become the `master` branch of this plugin. 
+
 How to... ?
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