Remove rules about reserved words

In 53b4173 we removed the ES5 guide which contains a lot of guidelines
that are no longer very relevant for us. Similarly, some folks have
raised the relevance of these rules about reserved words, given that we
are now living in an age where ES3 support has mostly waned and
transpilers such as Babel are widely adopted and pave over these issues.
This seems like a good opportunity to simplify.

Fixes airbnb#61

Author: lencioni

README.md

@@ -153,43 +153,6 @@ Other Style Guides
     const item = {};
     ```
 
-  <a name="objects--reserved-words"></a><a name="3.2"></a>
-  - [3.2](#objects--reserved-words) If your code will be executed in browsers in script context, don't use [reserved words](http://es5.github.io/#x7.6.1) as keys. It won't work in IE8. [More info](https://github.com/airbnb/javascript/issues/61). It’s OK to use them in ES6 modules and server-side code. jscs: [`disallowIdentifierNames`](http://jscs.info/rule/disallowIdentifierNames)
-
-    ```javascript
-    // bad
-    var superman = {
-      default: { clark: 'kent' },
-      private: true,
-    };
-
-    // good
-    var superman = {
-      defaults: { clark: 'kent' },
-      hidden: true,
-    };
-    ```
-
-  <a name="objects--reserved-words-2"></a><a name="3.3"></a>
-  - [3.3](#objects--reserved-words-2) Use readable synonyms in place of reserved words. jscs: [`disallowIdentifierNames`](http://jscs.info/rule/disallowIdentifierNames)
-
-    ```javascript
-    // bad
-    var superman = {
-      class: 'alien',
-    };
-
-    // bad
-    var superman = {
-      klass: 'alien',
-    };
-
-    // good
-    var superman = {
-      type: 'alien',
-    };
-    ```
-
   <a name="es6-computed-properties"></a><a name="3.4"></a>
   - [3.4](#es6-computed-properties) Use computed property names when creating objects with dynamic property names.