Make LoadModelFrom setup the object if possible.

Similar to PR #43, this allows for tombstone Vclocks to be setup inside a
new object.  The same error is returned as before, however if an object
was successfully fetched, it make sure the model is also able to be used
immediately.
Pull out the common model setting operation.

Pull out the common model setting operation into a separate function to make
it easier to update.
Merge pull request #44 from MJDSys/ModelTombstones

Similar to PR #43, this allows for tombstone Vclocks to be setup inside a
new object
Merge pull request #45 from tpjg/r1.4

Riak 1.4 features
Merge branch 'master' of https://github.com/tpjg/goriakpbc into r1.4