function initialize() {
  setOptionPageCSS();
  setCountry();
  setCountAndTopicList();
  setLocalizedTopicList();

  // Adds a custom topic on press of Enter key.
  $('newKeyword').onkeypress = addCustomTopic;
}
Initializes the options page by retrieving country, topics and count of
stories from local storage if present, else sets to default settings.