Trim Reddit

On the classic subreddit page, it adds an 'Old' button to the header, to help switching to old Reddit. On the old Reddit page, it adds a 'new' link in the header to switch back to classic Reddit.

The old Reddit page is changed to have a two pane window. List of articles are loaded on the left pane. Clicking an entry there loads the article on the right hand pane.

NOTE: this might break some Reddit features/views (things that I don't use but others might). As I learn more about such issues, I'll address them to the extent possible.