reactivity in the API

[gureckis]

there are several computed properties in the smilestore like isDone which are useful to check through project. rather than requiring components to import smilestore we want to let them import the smileapi.js and then access those computed properties. however, the way I tried this the first time doesn't preserve the reactivity tree. so when smileapi.js is initialized it looks up the value of the computed properties but then these values don't change later when the underlying state changes.