Update variable assignment to ES6 usage

[davidrbright]

Currently redux uses pre-ES6 variable assignment, as shown here. Per @gaearon it was due to flow failing on let/const a long time ago. The issue is no longer relevant now.

Will be working on a PR to update all variables today. It also seemed that there is interest in adding in semicolons. I could do that as well, any thoughts?

[markerikson]

Hi, thanks for following up on this.

I'm okay with a change from var to let/const, as it's reasonable for consistency given that we're using ES6 throughout the codebase. That said, although my own personal preference is to use semicolons, I'm also not keen on touching entire codebases just to update styles. Tends to make git blame rather useless. So, at this time I'd prefer to not introduce semicolons just for the sake of having semicolons.

[davidrbright]

Okay thanks for letting me know. I'll skip the semicolons as of now.