Better Rumor execution behaviour

Added

• Added a Running property to Rumor
• Added OnStart and OnFinish events to Rumor
• Added OnVarSet event to Scope

Changed

• Rumor.Run() will restart the script instead of throwing an exception if it
  is already running
• JumpToLabel and CallLabel are now exposed publicly, and work even if the
  Rumor has not been started yet
• Rumor constructors now provide a convenience method that takes a string
  directly
• You can now pass Rumor a scope to use

Removed

• The RumorCodeExample has been removed as it's potentially
  misleading/confusing