iframe should catch ⌘ events

[therewasaguy]

if iframe is focused (if you click on it while a sketch is running), ⌘'s don't work, for example ⌘R refreshes the page.

Maybe best handles key events with the same module as parent window, and also require it within debug-console.js (that sends messages from the iframe to the parent window).

[therewasaguy]

focus helps send the right events to the iframe: a5cf44a#diff-bdf2da6adcfb8d4a4d7a170c700937d3R73