Bump version to 3.0.0-beta.4

- Remove useless files
- Add a "catch" to "validate" promise
- fix CSS error in dev files

Author: Lionel Bijaoui

style.scss

@@ -38,7 +38,7 @@ html {
 }
 
 fieldset.vue-form-generator {
-	.form-group.half-width {
+	.form-element.half-width {
 		width: 50%;
 	}