use string keys for HTTP status codes in YAML

File that corresponds to Swagger specification must be correct JSON
file.
JSON doesn't allow integer keys.
YAML allows integer keys and parses "200: test" as {200: "test"} object.

Author: rutsky

versions/2.0.md

@@ -292,7 +292,7 @@ Field Pattern | Type | Description
     produces:
     - application/json
     responses:
-      200:
+      '200':
         description: A list of pets.
         schema:
           type: array
@@ -380,7 +380,7 @@ get:
   - application/json
   - text/html
   responses:
-    200:
+    '200':
       description: pet response
       schema:
         type: array
@@ -515,9 +515,9 @@ parameters:
   required: false
   type: string
 responses:
-  200:
+  '200':
     description: Pet updated.
-  405:
+  '405':
     description: Invalid input
 security:
 - petstore_auth:
@@ -874,7 +874,7 @@ A 200 response for successful operation and a default response for others (imply
 ```
 
 ```yaml
-200:
+'200':
   description: a pet to be returned
   schema:
     $ref: '#/definitions/Pet'