• require DT::F::B 0.75
  
• 'constructor' in specrefs instead of _normalize_day()
  
• removed _normalize_day()
  
• speed enhancement from internals cleanup
  
• fixed _normalize_week to properly handle week specified without a day of week
  
• fixed ISO week day tests (count from zero instead of 1 error)
  
• ISO8601 sections 5.3.1.1 - 5.3.1.3 and 5.3.3 - 5.3.4.2 maybe prefixed with 'T'
  
• doc update