Whitelist Heroku And Repl.it For WebSocket Connections

Heroku is a free cloud computing service, and is one of the first places many learners will set up a back end server. Repl.it is a site with a similar programming environment to KA, except that they allow multiple files per project, and will host back-end servers for users. Being allowed to make AJAX calls and WebSocket connections to these services would allow learners to create projects that stimulate conversation about back end development, which is a large hole in the KA computing curriculum at the moment.