Specify an array of preferred adapters 

I've added a possibility to pass an array of preferred adapter when creating a new Lawnchair object

    var store = new Lawnchair({
      name:'testing', 
      adapter: ['indexed-db', 'webkit-sqlite', 'dom'] }, 
      function(store) {
        // callback
    });

Lawnchair will initialize the first installed and valid adapter from the array, independently of the order in with the adapters were loaded. This permits to control fallback adapters much more easily.