code: function normalizeOptsKey(aval, basedir, pkg) {
  
      aval = aval || [];
  
      if (!u.isArray(aval)) {
        aval = [ aval ];
      }
  
      return u.map(u.compact(aval), function(val) {
        return normalize(val, basedir, pkg);
      });
  
    }
docs: normalize a single opts key