message: support header image in QuestionDialog
diff: @@ -31,6 +31,7 @@ export default createReactClass({
  danger: PropTypes.bool,
  focus: PropTypes.bool,
  onFinished: PropTypes.func.isRequired,
  + headerImage: PropTypes.string,
  },
  getDefaultProps: function() {
  @@ -63,6 +64,7 @@ export default createReactClass({
  <BaseDialog className="mx_QuestionDialog" onFinished={this.props.onFinished}
  title={this.props.title}
  contentId='mx_Dialog_content'
  + headerImage={this.props.headerImage}
  hasCancel={this.props.hasCancelButton}
  >
  <div className="mx_Dialog_content" id='mx_Dialog_content'>
  