Prefix all variables with module name.

Here is a patch.

In uninstall hook, this:

  // Comments variables.
  variable_del('gigya_comments_categoryid');
  variable_del('gigya_comments_container');

is actually not needed. These two will be picked up by

  // Delete variables.
  $variables = db_select('variable', 'v')
    ->fields('v', array('name'))
    ->condition('name', 'gigya%%', 'LIKE')
    ->execute()
    ->fetchCol();
  foreach ($variables as $var) {
    variable_del($var);
  }

earlier.

Adding to the patch...