F11 overrides toggle fullscreen binding

[gsmcmullin]

@FabianGeiselhart pointed out on #5 :

I think the F11 button is a really bad choice, b/c it toggles the fullscreenmode on most systems...

I know the possibility of creating own keybindings files, but I think overwriting an shortcut as important as F11 is not a good idea anyway...
Using F8, F9, and F10 instead of F9 F10 F11 would be better on my System

The default keybindings are chosen to match those used by Visual Studio Code:
https://code.visualstudio.com/Docs/customization/keybindings#_debug

@esden argued the merits of keeping keys compatible with other tools.

I'm leaving this issue open for comment. If there are strong opinions I'll consider changing the defaults. Users can also reconfigure the keys in Atom using a custom key map.

[esden]

As mentioned before, I am against the change, to keep the default bindings compatible to other packages.

Visual Studio: https://msdn.microsoft.com/en-us/library/aa239052(v=vs.60).aspx
Chrome Debugger: https://developers.google.com/web/tools/chrome-devtools/inspect-styles/shortcuts

That is why VSC has similar bindings. I am sure the F11 debugger binding was chosen before full screen key became a thing.