changed for shell-mode:

When ```cd``` is commanded without ```comint-mode``` stuffs, the emacs cannot track the working directory. It makes wrong completions, for example.
I think we should use ```comint-send-input``` for ```cd``` or any other commands changing the working directory, for ensuring the directory tracking of emacs (https://www.gnu.org/software/emacs/manual/html_node/emacs/Directory-Tracking.html)