Fix crash when attempting to union a relationship with a `nil` value. fixes #1195
Change log level for a specific mapping operation failure case
Fix implicit conversion warning in `RKDotNetDateFormatter`. closes #1198
Fix creation of duplicated managed objects when you map a `nil` source key path onto an indentification attribute. fixes #1194
Add missing interpolation value for assertion within search indexing
Fix issue where `NSManagedObject` instances that are invalid due to missing require relationship when finished mapping, but are made valid by connected relationships are deleted prematurely. fixes #1179
Add a warning if you violate the `save` expectations of `NSManagedObjectContext`. fixes #1185
Merge remote-tracking branch 'upstream/development' into development