code: function MongoStore(connection, options) {
  	if(arguments.length === 0 || typeof arguments[0] !== 'string') {
  		throw new Error('A valid connection string has to be provided');
  	}
  
  	TokenStore.call(this);
  
  	this._options = options || {};
  	this._collectionName = 'passwordless-token';
  	if(this._options.mongostore) {
  		if(this._options.mongostore.collection) {
  			this._collectionName = this._options.mongostore.collection;
  		}
  		delete this._options.mongostore;
  	}
  
  	this._uri = connection;
  	this._db = null;
  	this._collection = null;
  }
docs: Constructor of MongoStore
  @param {String} connection URI as defined by the MongoDB specification. Please
  check the documentation for details:
  http://mongodb.github.io/node-mongodb-native/driver-articles/mongoclient.html
  @param {Object} [options] Combines both the options for the MongoClient as well
  as the options for MongoStore. For the MongoClient options please refer back to
  the documentation. MongoStore understands the following options:
  (1) { mongostore: { collection: string }} to change the name of the collection
  being used. Defaults to: 'passwordless-token'
  @constructor