Modified Gear for Twist Lock Present

Two modifications to the gear for Twist Lock Present:

1) Tapered the mating to the spring, as my printer was squishing the first layer and making the hole a little too small

2) Added a slot / key to the top of the gear (where the topper attaches) to make it easier to preload the spring.

Standard print settings work fine -- 0.4 nozzle, 0.2 height, no supports, 2 walls, 3 top/bottom, 20% infill