new vim keybindings

imported latest vim keybindings from
https://github.com/marijnh/CodeMirror/blob/v2/keymap/vim.js
at commit ac0044fa30c50637b257fa2a2f9ea78e16d00da6
set keyMap: vim
included vim.js in notebook.html
vim keymap should work now
commented IPython.tooltip.remove_and_cancel_tooltip since it captured
the ESC-key and so ESC didn't work in "vim-mode"
tooltip still canceled