Split store methods related to API into lib module

[bericp1]

There are currently some methods I'm using repeatedly related to retrieving data from an API and that I can see using frequently in the future. They should be pulled into an external module in public/src/lib so that I can do something like the following:

var createAPIStore = require('create-api-store'); // `public/src/lib` has been added to the browserify search paths
var actions = require('./actions');
module.exports = createAPIStore('/api/items', {
  init: function(){
    this.listenTo(actions.reloadItems, this.reload);
    this.listenTo(actions.deleteItem, this.delete);
    this.listenTo(actions.addItem, this.add);
  }
});

[bericp1]

Related to #20