text: var levelup = require('./levelup');
  var levelupPack = require('./levelup-pack');
  var levelupPromise = require('./levelup-promise');
  
  var db = levelup()
  // serialization
  db.$use(levelupPack);
  // promises
  db.$use(levelupPromise);
  
  var k1 = [1,2,3], k2 = [4,5,6];
  var v1 = {name: 'foo'}, v2 = {name: 'bar'};
  
  db.open('./db-example').then(function(err) {
    return db.put(k1, v1);
  }).then(function() {
    return db.put(k2, v2);
  }).then(function() {
    return db.get(k2);
  }).then(function(val) {
    console.log(val);
    return db.get(k1);
  }).then(function(val) {
    console.log(val);
  }).catch(function(err) {
    console.error(err);
  });
  