Use native brotli when available and make iltorb & node-zopfli-es optional

[zetlen]

First off, thank you for maintaining this fork. Really appreciated.

Purpose

Make shrink-ray more fault-tolerant, so it can install and run without fatal errors on more versions of Node and build environments.

Ingredients

• Change hard dependencies on binary packages iltorb and node-zopfli-es to peer dependencies, so consuming apps can control their exact versions.
• Use native Brotli compression in NodeJS > 11.8 when available, and iltorb when not. When neither are available, fall back to gzip.
• Use node-zopfli-es when available, and fall back to gzip when not.
• Log warnings when fallbacks are in use.
• Update node-zopfli-es and mocha to comply with security audits.
• Add tests and proxyquire utility to simulate when modules are unavailable.

Compatibility

Tested locally on Node:

• v8.10.0
• v8.12.0
• v10.14.2
• v11.14.0

[coveralls]

Coverage increased (+0.08%) to 99.155% when pulling e4e9122 on magento-research:magento/make-binary-deps-optional into 3018a26 on Alorel:master.

[Alorel]

Hey, thanks for the PR. Looks good overall, just a couple of minor things. The Readme should also be updated with updated install instructions as the package now has peer dependencies.

CI is failing because Node 12 was just released and the native bindings haven't been updated for the new API version - that's fine and temporary.

[zetlen]

Thanks for your prompt response, @Alorel ! I've switched to process.emitWarning and added README details.

[Alorel]

Great, thanks 🙂 I can't make edits to a forked project, so as soon as you resolve conflicts with master it'll be good to merge (it should only be a node-zopfli-es version change in package.json)

[zetlen]

@Alorel I resolved the package.json conflicts last night and GitHub say there are no conflicts. Am I missing something?

[Alorel]

Hm, it's showing up as conflicting on github.com, but mergeable on the FastHub app

[Alorel]

Published as v4.0.0 - thanks again for the contribution!