Removed extra math

The elapsed's get cancelled in the numerator and denominator anyway. Probably doesn't jitter when followLerp = 0, but I didn't check for it.
Changed lerp to 0-1 value

Unsure about jittering right now
Undid flxrandom change

I'll get this right one day
Merge pull request #1 from HaxeFlixel/dev

Updating to recent dev
Cleanup, comments
Consistent across framerates

That's the plan, anyway.
Merge pull request #1220 from MSGhero/patch-1

Improvements to FlxCamera#followLerp