Book store HTML snippet box is too short.

In firefox, the default textentry size is too small to fit amazon affiliate html code. The fix is simple: add a maxlength to bookreview_store_snippet in bookreview.module:

    $form['bookreview_store_snippet'] = array(
      '#type' => 'textfield',
      '#title' => t('HTML snippet'),
      '#default_value' => variable_get('bookreview_store_snippet', ''),
      '#maxlength' => 512,
      '#description' => t('Enter the html snippet provided to you by the bookstore you\'d like to link to. The text "%ISBN"\ (without the quotes) will be replaced with the book\'s actual ISBN.'),
    );