Cacheing issues with production builds

[benmelz]

I was talking to Greg at lunch today, and he mentioned that he and some others have observed cacheing issues with the production map. Upon looking, our build process does not involve adding content hashes or anything of the like (it quite literally just serves each javascript file individually) which is probably causing those issues.

I would very much like to move to webpack to build things here, as that would also (I believe) allow us to bundle and serve dependencies directly as well instead of relying on CDNs.