[feature] fix contribution counts

**Purpose**
- Resolves [#1318](https://github.com/CenterForOpenScience/osf.io/issues/1318)

**Changes**
- Worked through finding this cause of this bug with @sloria.
- We discovered that auth was not being passed to ```_render_nodes``` inside of ```get_children```, which resulted in ```auth``` being equal to ```None``` inside of ```_rescale_ratio```, which resulted in "None Contributions" being displayed for each component. 
Can you make this assertion more specific? There are many values that aren't `0.0` that would make this test incorrect.