Update for HaxeFlixel/flixel#1220

Hasn't been merged yet in flixel.  Made this for if it does get merged in its current status.

Camera lerp is now a value from 0 to 1, 1 being the new default.  Checked everywhere, and this is the only time `followLerp` or the 4th parameter of `FlxCamera.follow()` was used.