Cleanup cloud functions

@josemontesdeoca this doesn't actually include the comment. i don't think we can fetch the one-to-many objects here (https://parse.com/docs/js_guide#queries-relational).

i think the best thing to do is have the "comments" just be posts themselves with a parentId, similar to what we have for goals. then the new code would be:

```
var query = new Parse.Query('Post');
query.equalTo('goal', createGoalWithId(goalId));
query.find().then(function(posts) {
    // group the posts and comments here based on the parentId
})
```