Unit tests for RemoteChange.buildFromMap

- Finding bugs where remote add operations are not being applied
RemoteChange.isModifyOperation check sourceVersion

Modify operations must have a source version and it will be greater than 0
RemoteChange.isAddOperation sourceVersion should be null or 0
RemoteChange test JSON needs cv property
Delete operations do not have a value
Merge pull request #43 from Simperium/remote-change-tests

Remote change tests