• Added ->then and ->else methods; like ->and_then but code is passed
  result directly instead of invocant future
  
• Added repeat { ... } foreach, otherwise argument to set final
  result and also handle empty lists
  
• Added repeat { ... } generate
  
• Turn repeat { ... } code block exceptions into failed futures
  
• Ensure that ->on_cancel returns $self (RT85134)
  
• Documentation / Phrasebook updates to demonstrate newly added
  features