Restore execution of Unit Tests via Rake
Update TESTING.md for 0.20.x and modern reality
Move Testing doc to more discoverable place
Add an exception if you try to create managed object contexts without adding a persistent store
Add error handling and use of `RKEnsureDirectoryExistsAtPath` so that Core Data examples work well for OS X as well as iOS
Fix a few issues identified via static analysis
Fixed documentation omission

The managed object store provides two managed object contexts, not two managed objects.
Fixed problems with initial implementation of temporary managed objects visitor. The implementation was under tested and only worked with a single relationship. refs #1001