1. Why did i pick Gargoyle Stoneplate? -Simple: I wanted that Twitch in the jungle could be as good as he is in his main job with his team: exceed and do a lot in teamfights. We all know that Twitch's life can be short if focused on a teamfight by a mobile assassin, for example (Cough, cough Fizz), so this is where this item shines, it gives Twitch 80 armor and 80 m.r. in teamfights to stay doing damage and slowing the enemy team with Frozen Mallet, which gives some health as well to back the resistances given by stoneplate AND if someone tries to burst Twitch instantly with tons of damage (Cough, cough Duskblade of Draktharr) out of nowhere, you can just activate the item and enjoy a LOT of damage absorption.

2. Why Twitch jungle? -Alongside the big efficiency of the "red buff n' lvl 2 gank" cheese start, Twitch can easily take the place of your actual ADC in teamfights and pickoffs where when he applies the slow from Frozen Mallet, they MUST burn mobility spells to get away. Just take care and beware of the enemy jungler since the most popular junglers right now are early game powerhouses ( Lee Sin, Elise, Shaco, Kha'Zix, etc.)

3. Jungle Route? Here's mine:
-Red Buff;
-Lvl up W and cheese gank (RISKY AND may lose you some time);
-Wolves;
-Blue Buff;
-Gromp;
-Scuttlecrab;
-Gank (if healthy).