emacs: remove goto-chg

I don't really use it, and when I do try to it doesn't really work.
emacs: enable winner mode
emacs: enable a few more helm things

autocomplete with C-:
browse mark ring with C-x C-SPC
show gtags stack with M-*
emacs: enable expand region

bind to C-=
emacs: don't need to bind C-h specially for ido

so that it acts as backspace. the global binding to
backward-delete-char(-untabify) does works in ido
emacs: remove multi-term

I don't use it. It (and term and ansi-term) aren't quite right. Maybe
I'll use shell or eshell one day.
emacs: use ctrl for windmove

doesn't clash with org-mode like shift does
emacs: add binding for helm-gtags-find-symbol

until I find a way to combine find-tag, find-rtag, and find-symbol, I
need a separate binding for each of them.
emacs: remove key binding for ff-find-other-file

I hardly ever use it
emacs: don't globally bind autocomplete shortcut

ac-complete-with-helm is only useful when autocomplete is enabled, so
bind it only in ac-mode-map, not using global-set-key
emacs: remove multiple-cursors keybinding

not sure which functions I want bound, and what keys I want them bound
to. so remove for the time being.