fix(spec): update OAS to 3.0.4 and fix core rules

Author: frankkilcommins

pom.xml

@@ -9,7 +9,7 @@
     <artifactId>swagger-petstore</artifactId>
     <packaging>war</packaging>
     <name>swagger-petstore</name>
-    <version>1.0.20-SNAPSHOT</version>
+    <version>1.0.21-SNAPSHOT</version>
     <prerequisites>
         <maven>2.2.0</maven>
     </prerequisites>