use valueForKeyPath to enable input dictionaries that need to access nested values
added a check for nil and NSNull in addWithDictionary
Merge branch 'master' of github.com:vokalinteractive/CoreDataManager-iOS
explicitly changed forKey to forKeyPath (thanks to Carl’s suggestion)
added tests for malformed data
fixed bug in which the unique identifier identified anyone
Merge pull request #31 from seanwolter/master

use valueForKeyPath and added safety check to addWithDictionary