Use pagination

[jsstevenson]

Right now, large queries (eg get_gene_list) are capped in the # of responses because of (reasonable) server configs. We need to make sure we're employing pagination to get all search results until they're exhausted.

[mcannon068nw]

Related, get_clinical_trials has a similar pagination issue through the clinicaltrials.gov API that we need to resolve going forward

[jsstevenson]

I thought get_gene_list was paginated because it's a round number, but actually the true number is round.

[jsstevenson]

Note also that we might be moving fda annotation out entirely in favor of the regbot package, which would obviate this