modify vimrc, improve accessibility

"Integrated Command vimgrep, search words in current path
map <C-f> :execute "vimgrep /" . expand("<cword>") . "/j **" <Bar>
cw<CR>

" plugin::BufExplorer {
" use F3 to open buffer list
map <F3> \be
" use c-j/c-k to switch buffer
map <C-j> :bn<cr>
map <C-k> :bp<cr>
" }