Crash when tapping row

[dkhamsing]

2015-03-23 08:33:56.350 RKGist[45281:1988533] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<RKGGist 0x7c055040> valueForUndefinedKey:]: the entity Gist is not key value coding-compliant for the key "timeStamp".'
*** First throw call stack:
(
    0   CoreFoundation                      0x0283d466 __exceptionPreprocess + 182
    1   libobjc.A.dylib                     0x024c6a97 objc_exception_throw + 44
    2   CoreFoundation                      0x0283d081 -[NSException raise] + 17
    3   CoreData                            0x0072598a -[NSManagedObject valueForUndefinedKey:] + 362
    4   Foundation                          0x01e77f28 _NSGetUsingKeyValueGetter + 104
    5   CoreData                            0x006bced3 -[NSManagedObject valueForKey:] + 131
    6   RKGist                              0x000757a7 -[RKGDetailViewController configureView] + 183
    7   RKGist                              0x000756c3 -[RKGDetailViewController setDetailItem:] + 131
    8   ...

[segiddins]

Please feel free to send in a PR with a fix.