Ability to Disable Lifecycle Events

[#1]

When the iOS SDK was 4.x was released the lifecycle events were enabled automatically but unlike 3.x they cannot be disabled. We aren't using them very much if at all right now and it's a bit unfair that they are there driving up our server calls when we didn't consciously implement them. We should be able to have a way to disable the calls if we wanted to.

[#2]

that's true, when i use ios sdk 4, I couldn't disabel lifecycle tracking, i think this might be a bug.