10X CD8 T Cell dataset example

[cornhundred]

10X released a dataset of ~100K CD8 T Cells, we should make an example notebook working with this data. We need to be careful to not add too much data to this repo however. Make a branch for this.

Dataset link: https://www.10xgenomics.com/extra/#whats-new?utm_source=Twitter&utm_medium=&utm_content=&utm_campaign=2019-Social-Twitter

https://support.10xgenomics.com/single-cell-vdj/datasets/3.0.2/vdj_v1_hs_aggregated_donor1