feat(node.js): remove attribute method

BREAKING CHANGE:

Method attribute does no longer exist. Use property attributes instead.

lib/node.js

@@ -1,7 +1,5 @@
 'use strict'
 
-const Attribute = require('./attribute')
-
 const htmlParser = require('htmlparser2')
 const domUtils = htmlParser.DomUtils
 const fs = require('fs')
@@ -151,24 +149,7 @@ class Node {
     }
 
     /**
-      * Returns or sets the attribute for the given key and value
-      * @param {string|Attribute} attr a key for getting an attribute or an attribute for setting the attribute on this node
-      * @returns {Attribute}
-      */
-    attribute(attr) {
-        const attributes = this.get().attribs
-
-        if (typeof attr === 'string') {
-            return new Attribute(attr, attributes[attr])
-        } else if (typeof attr === 'object') {
-            attributes[attr.key] = attr.value
-        }
-
-        return new Attribute(attr.key, attr.value)
-    }
-
-    /**
-       * Returns all attributes of this node
+       * Returns all attributes of this node. The returned object is live, so you can add or remove attributes as you wish
        * @returns {Object}
        */
     get attributes() {