What previously was the partial feeds/_entries.html.erb is now the view entries/index.html.erb

Deleted view show.html.erb that was redundant (it just rendered feeds/_entries, it's better to just render entries/index from the controllers).
Added (still non-functional) button "mark as unread" to each entry summary.
When opening an entry, a "mark as unread" button appears at the top of the summary. If the user clicks on it, the entry is marked as unread.