THRIFT-5003: Websocket Connection in Browsers with nodejs code

* changed this to self in forEach callback

* updated minimum node version to 8.16.2 (Maintenance LTS until December 2019)
changed ws_connection.js to work in the browser, with isomorphic-ws
added exports for `wsConnection`, `createWSConnection`, `createWSClient`

* added exports for WSConnection to browser.js

* extended the sample of nodejs code in the browser with webpack

* tested and updated node version to LTS 10.18.0 Dubnium
discussion based: https://github.com/apache/thrift/pull/1927#discussion_r358140463
5 files changed