Enable websocket compression in wsmc

[deathcap]

https://tools.ietf.org/html/rfc7692 Compression Extensions for WebSocket (December 2015)
https://www.igvita.com/2013/11/27/configuring-and-optimizing-websocket-compression/

This may allow disabling MC's own packet compression (compressionThreshold). It might also be faster (native browser support vs node deflate) than browserified node-minecraft-protocol's compression. Could also remove the uncompressedDataLength prefix field from the WSMC protocol (varint, 0 = uncompressed; no longer needed at all).

https://www.igvita.com/2013/11/27/configuring-and-optimizing-websocket-compression/#selective - could use this to only compress packets beyond a certain size threshold (just like MC's >256 bytes etc., so smaller (example: position update packets) are not needlessly compressed).

[deathcap]

Browser support:

• yes: Chrome M32+
• yes: Firefox https://bugzilla.mozilla.org/show_bug.cgi?id=792831
• open: WebKit https://bugs.webkit.org/show_bug.cgi?id=98840

Request for adding to caniuse (to conveniently track other browser support): Fyrd/caniuse#2216

[email protected] (websockets/ws#403) supports per-message compression