Every menu item is created with a path (File > Save). The functions are stored in a hash from (menu item path -> action) on the window. When an AtomMenuItem is selected, it looks up the action on the current window based on its path.
Move refresh handling to keyDown: method on AtomController. Eliminate custom handleInputEvent method.
NSApplication-sendEvent calls performKeyEquivalents on keydown events. Here I override sendEvent for keydown and forward the event to its window. This allows the web view to receive Command-H etc without key equivalents interfering. If the web view short-circuits the event, then the key equivalent will not be invoked. But it can let the event pass through and it ends up invoking the key equivalent anyway via a mechanism I don't fully understand. Apparently Cocoa tries to execute key equivalents after the web view finishes with the event? But it works great.
