Add clarification about inheritAttrs and class/style bindings (#1787) (#1969)

* Add note to the guide
* Update example, removing `class` attribute to avoid confusion

Author: leopiccionia

src/v2/guide/components-props.md

@@ -313,7 +313,7 @@ This can be especially useful in combination with the `$attrs` instance property
 
 ```js
 {
-  class: 'username-input',
+  required: true,
   placeholder: 'Enter your username'
 }
 ```
@@ -337,12 +337,14 @@ Vue.component('base-input', {
 })
 ```
 
+<p class="tip">Note that `inheritAttrs: false` option does **not** affect `style` and `class` bindings.</p>
+
 This pattern allows you to use base components more like raw HTML elements, without having to care about which element is actually at its root:
 
 ```html
 <base-input
   v-model="username"
-  class="username-input"
+  required
   placeholder="Enter your username"
 ></base-input>
 ```