begin Reachability only when starting for the first time and failing to download stories
On startup of app without internet we only want to automatically download new stories when we have no stories on the device.
Merge branch 'refs/heads/3.6/ipad-news' into 3.6/news-reachability
Combined showing refresh control code into separate method.
Added remove observer for kReachabilityChangedNotification
added check to see if www.mit.edu is reachable before making story request
renamed variables
Merge pull request #285 from MIT-Mobile/3.6/news-reachability

Fixes #283