WASM Brotli + Zopfli Encoding

[kristoferbaxter]

Branch has begun but there are two remaining issues.

1. Requires Node > 8. This might not be a technical issue, but needs communication.
2. https://github.com/dfrankland/wasm-zopfli and https://github.com/dfrankland/wasm-brotli do not support configuration, meaning we cannot use -q11 for brotli and are using the default iterations for zopfli.

[kristoferbaxter]

dfrankland/wasm-brotli#3

Filed issue in the wasm-brotli repo: looks like it currently only supports default parameters for encoding.