Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
I tested out a Attack speed Kennen and found out its not so bad. Electrical Surge and Thunder shuriken make a good combo for putting Quick marks on the enemy without waiting for CD's.
With the mix of having very high AP and AS Kennen is lethal for pushing lanes and or soloing one.
Purchase 1 - Boots, potion
Purchase 2 - Sorcers Shoes, potions
Purchase 3 - Rageblade
Purchase 4 - Sword of Devine
Purchase 5 - Void Staff
Purchase 6 Zhonya's ring
Purchase 7 ( if you wanna change out an item) - Soulstealer