Fix issue with AFMMRecordResponseSerializer threading

I created a new pull request with some additional error handling using the built in debugger. @jonbrooks please take a look.
Sorry - I was away and didn't have a chance to respond to this. I wasn't aware of the complexities around parent/child contexts either.  And I'll second Josh's statement about learning about CoreData.  I've learned a lot from both this issue and MMRecord's source.  

From a code evolution standpoint, the refreshObject solution seems like a reasonable step forward.  There may still be problems with more complicated CoreData setups, but at least it will prevent crashes in the basic cases.  Some thought should to be given on whether to merge changes or not.  

I don't have a clear picture of what the other solution you mention would look like - or what problems it may have - but on the face of it, it seems like that could be a better long term solution.  But again, I don't see any reason not to move forward with the refreshObject one in the interim.