Move resetStack as reset in CoreDataStack

[Liquidsoul]

Pull request checklist

• All tests pass. Demo project builds and runs.
• I have resolved any merge conflicts.
• I have followed the coding style, and reviewed the contributing guidelines.

This fixes resetStack part of issue #69

What's in this pull request?

• resetStack is now a static method of CoreDataStackFactory

[jessesquires]

Thanks @Liquidsoul ! 🎉

Annnd, I'm dumb. Looking at this, I was thinking "this feels weird." Then, I realized that this makes more since as an instance method on CoreDataStack. What do you think?

We can update the method signature to: reset(onQueue queue: completion: )

Sorry for the churn! 😄

[Liquidsoul]

My bad, I should have listen to my fingers when I tried to remove the stack: argument and it did not work.
I should have stopped right there and think 😅
I'll change this.

[jessesquires]

Also, a quick note: this means the stack will pass itself to the completion block. Might be a bit odd, but I think this is good. Then you won't have to capture the stack in the closure via self.stack if you need to do extra work after the reset.

[Liquidsoul]

Just updated and rebased the branch. Do you want me to squash the commits together?

[jessesquires]

Looks awesome! 🎉 I'll squash via github. 👍