Tiny update. Simply added compatibility with Gamerules Gadget by Stik'.

Made the mod default to player-only assimilation when no game rules are set (meaning games started prior to having the mod)
Default game rule (when starting a new game) is still for allowing it for both player and AI.

• Updated for compatibility with 1.9
  
• Added an extra rule so Cultural Assimilation is only available to players
  
• Changed ai_cultural_hybridization_interaction (from 00_culture_interactions.txt) so AI won't check if their culture is the target culture's parent/child or shares a heritage