Update django CMS version in README

Author: fsbraun

README.rst

@@ -12,7 +12,7 @@ There are two different ways to manage forms with **djangocms-form-builder**:
 
    Form actions can be configured by form. Built in actions include saving the    results in the database for later evaluation and mailing submitted forms to   the site admins. Other form actions can be registered.
 
-2. Works with **django CMS v4** and **djangocms-alias** to manage your forms centrally. Djangocms-alias becomes your form editor and forms can be placed on pages by referring to them with their alias.
+2. Works with **django CMS v4+** and **djangocms-alias** to manage your forms centrally. Djangocms-alias becomes your form editor and forms can be placed on pages by referring to them with their alias.
 
 3. **Registering an application-specific form with djangocms-form-builder.** If you already have forms you may register them with djangocms-form-builder and allow editors to use them in the form plugin. If you only have simpler design requirements, **djangocms-form-builder** allows you to use fieldsets as with admin forms.