Image-sequencer: Changing asynchronous callbacks of Sequencer Object to Promises

[blurry-x-face]

As of now we support ES6 but we still have so many callbacks and callback hells! We should change them to Promises because promises:

• *[x] Allow cleaner and better, functional code with less error-prone boilerplate
• *[x] Are easy to debug
• *[x] Provide catching mechanism which are not in callbacks
• *[x] Promises are built over callbacks

[blurry-x-face]

@publiclab/is-reviewers @jywarren @HarshKhandeparkar
What are your views?

[Divy123]

I think this can be a great step towards easy debugging and attaining a more managed codebase, easier to handle. What do you think @jywarren ?

Also, @blurry-x-face do you want to work on this one?

[blurry-x-face]

Yes! I want to work on it!

[Divy123]

I think you can go ahead after listening to @jywarren .