consider removing all data from DocumentRefs

[scien]

problem state i just discovered...

• data is updated
• ref catches update and changes its @data
• ref emits event
• event handler used ref.get('property').val() // ISSUE: property was out of date
• ref updates @document.data

ref.get passes the document and the path, it ignores local data, so the document data had to be updated before emitting events. I can't think of any benefit to duplicating the data in the DocumentRef at all now. I think the val() call should just always ask the document what the value at its path is.

only tricky thing i can think of is if you have a ref listener it would have to tell the document to update that part of its data. going to sit on this for a little bit and think it over.