Chord should pass an event to the function callback.

[ahsteele]

Chord needs to pass the keyboard event to its function callbacks. The primary use case is the need to event.preventDefault(). Reason for the need to prevent default functionality is when browsers like Firefox do silly things like hijack the forward slash for "quick find": https://support.mozilla.org/en-US/kb/keyboard-shortcuts-perform-firefox-tasks-quickly. #sigh

[rheone]

Issues taken care of by commit 61927ad8fa7421ff06a7fe4a6fa690f405770da1

Explicit unit testing still required, but event is now available to call back method.