title: Validate Json Schema
body: <p>I'm getting an error when using <a href="https://github.com/fge/json-schema-validator" rel="nofollow">json-schema-validator</a> API v4. 
  I try to do : </p>
  
  <pre><code>final JsonValidator validator = new JsonValidator(JsonLoader.fromPath("schema.json"));
  ValidationReport report = validator.validate(data);
  </code></pre>
  
  <p>but every time I get an error : # [schema]: unknown keyword contacts</p>
  
  <pre><code>schema.json :
  {
      "contacts": {
          "description": "The list of contacts",
          "type": "array",
          "optional": true,
          "items": {
              "description": "A contact",
              "type": "object",
              "properties": {
                  "givenName": {
                      "description": "Person's first name",
                      "type": "string",
                      "maxLength": 64,
                      "optional": true
                  },
                  "familyName": {
                      "description": "A person's last name",
                      "type": "string",
                      "maxLength": 64,
                      "optional": true
                  }
              }
          }
      }
  }
  </code></pre>
  
  <p>Regards</p>