Force callee to pass the context

Setting this default forces a dependency on SuperCoreDataStack, it also encourages very bad practice via blase/naive management of
the context. The callee can still use this class, but should be forced to pass in the context. Related to michaelarmstrong#25

SuperRecord/NSFetchedResultsControllerExtension.swift

@@ -99,7 +99,7 @@ public extension NSFetchedResultsController {
         return superFetchedResultsController(entityName, sectionNameKeyPath: sectionNameKeyPath, sortDescriptors: sortDescriptors as [AnyObject], predicate:nil, delegate: delegate)
     }
 
-    private class func superFetchedResultsController(entityName: String!, sectionNameKeyPath: String?, sortDescriptors: [AnyObject]?, predicate: NSPredicate?, delegate: NSFetchedResultsControllerDelegate, context: NSManagedObjectContext! = SuperCoreDataStack.defaultStack.managedObjectContext!) -> NSFetchedResultsController {
+    private class func superFetchedResultsController(entityName: String!, sectionNameKeyPath: String?, sortDescriptors: [AnyObject]?, predicate: NSPredicate?, delegate: NSFetchedResultsControllerDelegate, context: NSManagedObjectContext!) -> NSFetchedResultsController {
 
         let fetchRequest = NSFetchRequest(entityName: entityName)
         fetchRequest.entity = NSEntityDescription.entityForName(entityName, inManagedObjectContext: context)