osteosarc 0.13.0

A simpler site, and less code (#75).

• The home page is the overview. Concepts is folded into a short "How the data
  fits together" there, linking to each topic's page.
• Removed, now that the OpenVax libraries take their reads from openvax-v1:
  • osteosarc.regional_corpus;
  • the generators in legacy_fixtures (generate, pack, verify, export_fixture and
    their helpers) and cohort_bundle (generate_cohort_bundle, retrieval_regions);
    the functions Isovar and Vaxrank import stay;
  • osteosarc.bundles.generate_panel; osteosarc test-data make --recipe, or
    generate_bundle, does the same;
  • osteosarc.records.sam_digest, and SAM-text record identities in recipes;
  • osteosarc.reads.subset_templates, a random sample that make_bundle's balanced
    sets replace;
  • reading bundles made by osteosarc 0.2 or earlier, which now says to make them
    again.
• The frozen SV test recipe moves from the package into tests/data.