[help] FSM considers insert mode.
[cm] CodeMirror signals vim-keypress at exitInsertMode.
[help] 'cc' command arrives at _insert state.
[mode] Move mode displayer inside help.js and FSM.
[help] 'ciw' and 'cw' keys go to insert mode.
[help] Remove mode variable from CommandHelper.
Merge branch 'insert-mode' into develop