Flat data for users at each stage module

### :fire: Adds in `flatten:true` to the `query-params` of journey_series module :fire: 
### :fist: Checks for `group_by` before flattening :fist: 
- If we don't have a `group_by` value in the `data_source` we shouldn't attempt to regroup the data by this field.
- It looks like data comes out 'flat' if we don't have a `group_by` value.

![](http://41.media.tumblr.com/c0acb7186db24cff6537ed379db051fd/tumblr_n9vf34Y74r1qcwuqfo1_500.png)