Fix crash due to execution of `RKDeleteInvalidNewManagedObject` from outside of the dispatch queue of the `NSManagedObjectContext` that owns the object. fixes #1251
Add countermeasure to avoid crash in `cxx_destruct` during deallocation of mapping result
Merge pull request #5 from moneytree/hotfix/mutating-crash

Cherry picked another commit from RK with crash problem (Crashlytics issue #10)