intronIC v1.3.6

• Deal with edge-case issue where a gene feature has children
  exon/CDS features in a direct parent-child relationship.
  Previously, this would bypass the recursive search for introns used
  by get_introns() due to an early exit, resulting in preferential
  inclusion of introns whose Parent attribute was the gene itself
  rather than a child transcript.
• Remove old code/fix whitespace
• Update __version__ paradigm
• Remove Physarum-specific branch-point PWM code