[FIX] Non-Unique Filename Hashing

[lukeed]

What kind of change does this PR introduce?

Fixes #459

Did you add tests for your changes?

N/A

Summary

Apparently, since October 2017, an underlying dependency has had an incompatibility with Webpack's ModuleConcatenationPlugin. Because of this, all files and chunks were producing the same [hash] and [chunkhash] values.

Before removing, I tried adjusting the output patterns, but that didn't change anything.

Luckily, it seems as though we weren't actually using this plugin in the way it was intended, so simply removing it worked.

We're now relying on Webpack's own hashing algorithm, which is probably a safe(r) bet since that's one of its first-class priorities.

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@developit This will have to go out ASAP since everyone is producing repetitive builds. I suspect this is also playing a role in the SW issues.

[prateekbh]

doesn't webpack rely on -p/NODE.ENV===production flag to add the hashes?

[lukeed]

Yes, but we only care about preact build since that's the only time hashing is added to files. And build flags a production build.

(The DevServer is in-memory, no files added to disk.)