added safe context to managedObjectOfClass:inContext:
Merge pull request #22 from chillpop/master

Convenience factory methods for managed objects and ability to use an in-memory store
Merge branch 'master' of github.com:vokalinteractive/CoreDataManager-iOS
made sure safeContext: is applied to new entity methods
Merge pull request #23 from seanwolter/master

added safeContext: check to inert new entities methods and updates Carl's convenience methods to use contextOrNil