Implementing a detail view for posts

[bkesk]

I have implemented a detail view for individual blog posts, and added tests that cover the changes. A summary of changes:

• The index view now shows only the first 200 characters of each post
• In the index view, a link to the detail view is included at the end of each post body
• The title of each post in the index view links to the detail view
• The "Bad Apps Blog" title is clickable, and returns the user to the index view
• In the detail view, an authenticated user is given a link to the edit view if they wrote the post that they are viewing