feat: Provide promisified method versions

An easy way to do it is to query args length, and then return a promisified version like:

     const util = require('util');
     return util.promisify(User.get)(options);

[diosney]

@fishcharlie

1- OK, I will take that into account for the next issue, this seemed so easy for me to be explained that I thought filling the whole template was too much for two lines of explanation.

Nevertheless, it could be great if you educate us instead of trigger a defensive action by just closing it, since if I took the time to fill an issue at least is a sign that I want the project to be better.

2- Nice! It could be good if that is added to the documentation, since all examples have the callback pattern and there is no immediate clue that Promisified versions are available.

(all have it but populate, which is a special case and I thought that was only for it).

[fishcharlie]

@diosney

1. The issue template was not filled out for this issue which is a strong requirement of filing issues for Dynamoose. At the very top of the issue template it says Not filling out ALL of the relevant fields in this issue will cause your issue to be closed.
2. This is already implemented into Dynamoose. If you don’t pass in a callback into a method, Dynamoose will return a promise. Using util.promisify isn’t required.