Enables setting two character shortcuts (e.g. jk) to exit insert mode

Enables setting two character shortcuts (e.g. jk) to exit insert mode (partially addressing #12) by:
1) enabling setting CodeMirror.Vim options in user.behaviours 
2) updating vim.js to latest from https://github.com/marijnh/CodeMirror/blob/master/keymap/vim.js.

Wasn't sure if it's just best to commit the .cljs changes, committed all so others could easily use before it gets merged. Let me know if you want me to remove the vim.js, vim_compiled.js and vim_compiled.js.map or other changes.

Here's the relevant changes in the :+ :editor map of user.behaviors to enable two character esc:

    (:lt.plugins.vim/set-vim-option {"enableInsertModeEscKeys" true,
                                               "insertModeEscKeys" "jk"
                                               "insertModeEscKeysTimeout" 200}) ;; 200ms is actually the default so not strictly necessary



Thanks for your great stuff Chris! You're doing very important work, excited to see Aurora.