Fix/1291 inject works again

Fixed #1291
Injection broke god knows how long ago. This puts it back in place, but you can control panels in two ways:

1. jsbin.com/?html,js,console - shows those 3 panels
2. jsbin.com/?hmtl=<body>&js=(function() { alert("Hello world")})()&output - shows HTML, JS and output panel, and injects into the HTML & JS