docs: function similar(lhs, rhs) {
    if(Math.abs(lhs.length - rhs.length) > SIMILARITY_LENGTH_THRESHOLD) return;
    var map = _.reduce(lhs.split(''), function(m, c) {
      m[c] = true;
      return m;
    }, {});
  
    var cmn = _.reduce(rhs.split(''), function(m, c) {
      return m + !!map[c];
    }, 0);
  
    return (rhs.length * SIMILARITY_LEVEL_THRESHOLD) < cmn;
  }