console.log a message if there is an incorrect combination of attributes

platinum-sw-fetch.html

@@ -125,6 +125,9 @@
         };
         if (this.path && this.handler) {
           params.route = [this.path, this.handler, this.origin];
+        } else {
+          console.log('The following platinum-sw-fetch element will not have any effect. ' +
+            'Both the "path" and "handler" attributes must be set.', this);
         }
         resolve(params);
       }.bind(this));

platinum-sw-import-script.html

@@ -49,6 +49,9 @@
         var params = {};
         if (this.href) {
           params.importscript = this.href;
+        } else {
+          console.log('The following platinum-sw-import-script element will not have any effect. ' +
+            'The "href" attribute must be set.', this);
         }
         resolve(params);
       }.bind(this));