Updated required field according to the json schema spec.

Author: delvedor

index.js

@@ -158,7 +158,7 @@ function buildObject (schema, code, name) {
       `
     }
 
-    if (schema.properties[key].required) {
+    if (schema.required && schema.required.indexOf(key) !== -1) {
       code += `
       } else {
         throw new Error('${key} is required!')

test.js

@@ -263,13 +263,13 @@ test('object with required field', (t) => {
     type: 'object',
     properties: {
       str: {
-        type: 'string',
-        required: true
+        type: 'string'
       },
       num: {
         type: 'integer'
       }
-    }
+    },
+    required: ['str']
   }
   const stringify = build(schema)