#5 Added new models

 - Issue model - Will represent an issue. Will have attribute Editor's
   note
 - Article - Will represent an article. Will have title, title link, description and
   links. It will belong to an issue.
 - Event - Will represent an event. Will have title, title link, description and
   links. It will belong to an issue.
 - Link - Will have anchor text and url. Belongs to article or event.
   Can be used when you want to display multiple links in the
   description other than title link.