Add command to update gene ranks

This includes model updates and migrations.
Accept sample labels as arguments to the gene-ranks command
Add script to call gene-ranks command after samples load

This will need to be added as a cron job like the recalculate_allele_frequencies script is used now.
Add httpretty as a test dependency
Add test fixtures for 3 samples

These correspond to locus_1 from the disease_loci folder in the varify-demo-data repo
Add a mock log handler for aggregating log messages
Add tests to INSTALLED_APPS in test settings
Add beginnings of tests for the gene-ranks commands

So far, this just accounts for missing settings and error responses from the phenotype endpoint
Add earlier escape condition if hpoAnnotations is empty
Gracefully handle errors in looking up hpo_id value
Add more tests for bad/missing data from the phenotype endpoint
Use correct comparison operator for checking if sample is up to date
Add setting for disabling auto creation of world cohort on sample update
Set VARIFY_AUTO_CREATE_COHORT to False for GeneRanksTestCase
Add a test for error-free loading cases
Log a warning when gene list is empty and update gene rank url format
Combine all patches into a single registration method
Test the case of a valid phenotype and bad genotype endpoint response
Update load test case to use patched gene rank endpoint
Save the ResultScore in a more logical manner