[chore] Pin zuul version
[chore] Pin zuul version

The CI fails with the new version: https://travis-ci.org/socketio/engine.io-parser/jobs/448690970

> /home/travis/build/[secure]io/engine.io-parser/node_modules/zuul/bin/zuul:332
>             throw err.message;
>             ^
> internet explorer@8: [eval("(window.zuul_msg_bus ? window.zuul_msg_bus.splice(0, 1000) : []);")] Not JSON response

Automattic/engine.io-parser,socketio/engine.io-parser,socketio/engine.io-parser,socketio/engine.io-parser