Fix for issue #1500, blog title not showing in reader

Trying to fix issue #1500 with these changes:

Fix: ```blogName``` was being set to nil in ```updateFromRESTDictionary:```.

Fix: Now that it was no longer nil, ```blogName``` was replacing ```authorString``` instead of showing underneath the author's name.
 
Add: ```blogNameForDisplay``` to show blog name under the author.