Rework missed helper

[chapel]

After some testing and using the existing implementation, I have found it to be inadequate and not very intuitive. Requiring more code to do something fairly simple, multiple loops at times.

Instead of an object or an array, it will simply be an object like so:

missed = {
    keys: [
        'key'
      , 'key2'
    ]
  , save: function(key, value) {
      // Save value to appropriate key
    }
}

This would allow usage like so:

db.find(missed.keys, function(err, values) {
  if (err) return done(err)

  for (var i = 0; i < values.length; i+=1) {
    missed.save(values[i].key, values[i])
  }

  done()
}

I could even get rid of done, and have missed.done(), but I think having a clear done() function makes more sense in Node.js conventions.