yas/minor-mode name fixed

Backtrace was:

Debugger entered--Lisp error: (void-function yas-minor-mode)
  yas-minor-mode(1)
  run-hook-with-args(yas-minor-mode 1)
  (cond (elpy-mode (if buffer-file-name (progn (set (make-local-variable (quote ffip-project-root)) (elpy-project-root)))) (set (make-local-variable (quote eldoc-documentation-function)) (quote elpy-eldoc-documentation)) (add-to-list (quote ac-sources) (quote ac-source-elpy)) (add-to-list (quote ac-sources) (quote ac-source-elpy-dot)) (run-hook-with-args (quote elpy-default-minor-modes) 1)) (t (kill-local-variable (quote ffip-project-root)) (kill-local-variable (quote eldoc-documentation-function)) (setq ac-sources (delq (quote ac-source-elpy) (delq (quote ac-source-elpy-dot) ac-sources)))))
...