Merge pull request #293 from barijaona/bugfixes

Vertically center text in the folder list and in the article list
Safety measure on GoogleReader

Cf Skripach crash logs at http://www.cocoaforge.com/viewtopic.php?f=18&t=26573&sid=38253d1334b27782d22d2f31daa258a9#p138418
Safety measure for transactions ; improve refresh indicator

After seeing http://www.cocoaforge.com/viewtopic.php?f=18&t=26578
Serialize uses of the jsonDecoder

As recommended by JSONKit documentation