Refactor serum_titers rule to automate QC (#21)

* start re-factoring `serum_titers`

* plot NT50 vs midpoint correlation

* fully implemented `serum_titers`

* `black` formatting

* update `aggregate_titers` to work w new `serum_titers`

* update `.gitignore` and track results

* fix `sera_override_defaults`

* add to `manual_drops` in example

* further adjust qc_exclusions in example

* compute one sera titers as nt50 rather than midpoint

* update expected titers for test

* code formatting

* rebuild test example docs

.github/workflows/test.yaml

@@ -55,9 +55,9 @@ jobs:
           && snakemake --software-deployment-method conda -j 2
           && cd ..
 
-#      - name: test titers as expected
-#        shell: bash -el {0}
-#        run: cd test_example && python test_titers_as_expected.py && cd ..
+      - name: test titers as expected
+        shell: bash -el {0}
+        run: cd test_example && python test_titers_as_expected.py && cd ..
 
       - name: upload results in case of error
         uses: actions/upload-artifact@v3