sm_jetpack and other movement plugins don't trigger protection disable

[foobarhl]

I noticed a player wasn't exiting spawn protection when using sm_jetpack out of spawn. We should look into detecting use of third party plugins.

I'm hesitant to implement movement detection since spawning on gibs or other debris causes movement when the player didn't necessarily intend to move.

[foobarhl]

Issue #7 addresses this.