Override escape with jk for use with atom's vim-mode

init.coffee

# ~/.atom/init.coffee

atom.commands.add 'atom-text-editor', 'exit-insert-mode-if-preceded-by-j': (e) ->
  editor = @getModel()
  pos = editor.getCursorBufferPosition()
  range = [pos.traverse([0,-1]), pos]
  lastChar = editor.getTextInBufferRange(range)
  if lastChar != "j"
    e.abortKeyBinding()
  else
    editor.backspace()
    atom.commands.dispatch(e.currentTarget, 'vim-mode:activate-normal-mode')

keymap.cson

'atom-text-editor.vim-mode.insert-mode':
    'k': 'exit-insert-mode-if-preceded-by-j'