add --store-read-ids and --read-ids-whitelist options

[lldelisle]

As the #170 is not ready and I needed these options quickly, I implemented them on the current version.
I tested with:

cite_seq_count/__main__.py -R1 tests/test_data/fastq/correct_R1_with_cell_barcode_mm.fastq.gz -R2 tests/test_data/fastq/correct_R2.fastq.gz -t tests/test_data/tags/pass/correct_3.csv -cbf 1 -cbl 16 -umif 17 -umil 26 -wl tests/test_data/whitelist.csv -cells 1 --store-read-ids --read-ids-whitelist tests/test_data/whitelist_single.csv

This PR is just here to tell people that this version exists. @Hoohm you don't need to incorporate these changes. I don't think I will be able to write test for these options, so you can close this PR.