rename: use original word's length for replacing
rename: use original word's length for replacing

Ref: https://github.com/davidhalter/jedi-vim/pull/403#discussion_r29548013

wilywampa/jedi-vim,aliev/jedi-vim,clavery/jedi-vim,jmartiuk5/jedi-vim,pze/jedi-vim,genzj/jedi-vim,FBruynbroeck/jedi-vim,davidhalter/jedi-vim,maxamillion/jedi-vim,itchyny/jedi-vim