hidden exception

If the ruby client is used with ripple; using an association callback that fails;  this line will display the message of the failure; but hides exception trace showing where in the callback the underlying exception failed.

https://github.com/basho/riak-ruby-client/blob/master/lib/riak/client.rb#L477

After max tries completes; could the ruby client raise the underlying exception instead of just the message?

https://github.com/basho/riak-ruby-client/blob/master/lib/riak/client.rb#L482