function-args.el (moo-complete): fall back to semantic
function-args.el (fa-tfunction->fal): do only functions
function-args.el (moo-tag->str): generalize

* function-args.el (moo-tag->str): Works for function, variable, type.
  (moo-tag-variable->str): New function.
  (moo-tag-type->str): New function.
function-args.el (moo-stype->tag): simplify
README.md: add