Ladybug

Summary

• Fix custom_cluster_pathway_enrichment() to accept a list of lists as input.
• Use filtered feature-to-gene map to perform pathway enrichment.
• In cluster_pathway_enrichment(), remove pathway enrichments driven by a single gene
  for consistency with the landscape paper.

What's Changed

• final prep for workshop by @nicolerg in #37

Full Changelog: v1.4.0...v1.4.1