Don't mutate options parameter when updating table

[randyxli]

Thanks for the awesome package!

I noticed that table#update was unexpectedly mutating the options parameter, which can cause silent bugs. For example, if we want to log all the times where an item we want to update does not exist, we might write something like:

let options = { expected: { id: { Exists: true }}};
for (let model in modelsToUpdate) {
  model.update(updateObject, options, function(err, updatedModel) {
    if (err) {
      logger.warn('Model not found');
    }
  });
}

This code does not log as intended because the expected key is deleted from the options object after the first update. In this PR I propose making use of lodash to avoid mutating the options parameter and simplify the code slightly. Thanks for looking!

[coveralls]

Coverage decreased (-0.008%) to 98.654% when pulling 7f85915408d017e07fefc169587f75152803a60e on randyxli:options-mutation into d327665b1ad475d1b2aba4ae4dd3a86db8b34685 on clarkie:master.

[coveralls]

Coverage decreased (-0.008%) to 98.654% when pulling 7f85915408d017e07fefc169587f75152803a60e on randyxli:options-mutation into d327665b1ad475d1b2aba4ae4dd3a86db8b34685 on clarkie:master.