Suggest adding key binding in Xcode, not System Preferences

[JosephDuffy]

Adding the keyboard shortcut via System Preferences has the downsides of being specific to each Xcode version (it seems to list every Xcode version I have installed, although I've not verified if they're all applied separately) and also requiring the exact name of the menu item.

Xcode's Preferences => Key Bindings includes the action from the menu and seems to avoid these issues, so it might be easier to direct users to using this option?

[orchetect]

Already addressed in #17 and will be in next release. Repo README already used Key Bindings screenshot and the app now adopts it as well.

[aheze]

Yep thanks @orchetect for that. I'll recompile and release in a bit — want to try out syntax aware splitting first. If that doesn't work, I'll just go ahead and release anyway.