Fix duplicate category definition

This commit removes the duplicate category definition to fix the Xcode
warning.
Cast relationship objects to fix Compiler Error

With the addition of Facebook's Bolts, objectID on `id` now correlates
to a String, thus the isTemporaryID method didn't exist. Properly
casting the object fixes this.
Merge pull request #47 from sbonami/Cast-relationship-objects-to-fix-compiler-error

Cast relationship objects to fix compiler error