Make Emacs Alt-/ behave more like RubyMine: toggle comment on region or toggle comment on line (and then move down to next line).

toggle-comment.el

(defun toggle-comment-for-line-or-region (arg)
  "Make Emacs Alt-/ behave more like RubyMine: toggle comment on region or
toggle comment on line (and then move down to next line)."
  (interactive "*P")
  (let ((initial-mark-state (and mark-active transient-mark-mode)))
    (unless initial-mark-state
      (mark-line))
    (comment-or-uncomment-region (region-beginning) (region-end) arg)
    (unless initial-mark-state
      (next-line))
    (font-lock-fontify-buffer)))

(global-set-key (kbd "M-/") 'toggle-comment-for-line-or-region)