v1.13.1

• modularized bit-filter-seqs-by-length and added a test for it
  • also changed the name to bit-filter-fasta-by-length, though i'm retaining a stub for the old name so it still works when called that way too
• modularized bit-summarize-column and added tests
• added a temp fix for the latest megahit osx-64 build not working (see smk/envs/assemble-osx-64.yaml; if that's gone it was no longer needed and removed in the future)
• fix to bit-summarize-column when standard input is only one column (was erroring out before)