Bug 1023663 - [User story] Calendar day view should start at 8 AM r=millermedeiros

Currently, the patch is for ui review. It is not ready for code review.
I find it really weird that we have 2 methods that does basically the same thing and that have so much shared logic.. I think this could be better abstracted.. I think we need a method that receives a date object and returns the `scrollTop`, so you could write it like:

```js
_scrollDayEventsWrapper: function(date) {
  this.changeDate(date, {
    scrollTop: this._dateToScroll(date),
    animated: true
  });
},

_scrollDayEventsWrapperOnlyForToday: function(date) {
  this.changeDate(date, {
    scrollTop: this._dateToScroll(date, {onlyToday: true}),
    animated: true
  });
}
```