add yasnippet stuff into README
add yasnippet stuff into README

zuoshifan/emacs.d,zuoshifan/emacs.d,zuoshifan/emacs.d,zuoshifan/emacs.d,zuoshifan/emacs.d,YangXin/emacs.d,zuoshifan/emacs.d,zuoshifan/emacs.d,YangXin/emacs.d,zuoshifan/emacs.d,zuoshifan/emacs.d