Custom villager spawning

So I have a survival server in 1.8 and we want create a villager with a custom trade. The trade will be receiving one haste II potion for 15 minutes if you pay 5 diamond blocks. I have not found a way to add in the effects for haste. This is the command for spawning the potion I want: /give @p minecraft:potion 1 13 {CustomPotionEffects:[{Id:3,Amplifier:1,Duration:30000}]} however I do not understand how to put it in the command to spawn the villager, here is what I have so far: /summon Villager ~1 ~ ~ {Invulnerable:1,CustomName:Haste-Trader,Proffession:3,Career:6,Offers:{Recipes:[{maxUses:1000000,buy:{id:diamond_block,Count:5},sell:{id:potion,Count:1}}]}}
How do I change the normal potion to be a haste II for 25 minutes? please help