Merge pull request #48 from l0rb/dev

removed useless class field
FlxButtonPlus: small cleanup
Consistent spacing
Update CHANGELOG.md
Update haxelib.json
FlxNapeVelocity.stopVelocity(): remove duplicated logic
Compatibility with FlxCamera.defaultCameras (HaxeFlixel/flixel#895)
FlxClickArea: get rid of dynamic callback, use Void->Void instead (HaxeFlixel/flixel#805)

- onUp is now public and Void->Void
- removed _onUpParams
- removed setOnUpCallback()
fix for issue #49
Refactored StarFieldFX into FlxStarField2D and FlxStarField3D
Move PNGEncoder to flixel.addons.util
Small cleanup for FlxBullet and FlxWeapon

- removed FlxBullet.xGravity and yGravity (use acceleration instead)
- removed FlxBullet.maxVelocityX and maxVelocityY (use maxVelocity instead)
Update to use the new rendering conditionals
Update for HaxeFlixel/flixel@e498efdbc3dc4eb9ba476c612b7ca6040d8f238e
FlxNapeState: fix nape debug positioning with a camera target and zoom levels different than 1
Update for HaxeFlixel/flixel@26ee513567f0debdc8ed84a2177888564b525d73
Use FlxPoint.get() and FlxRect.get() everywhere
Update for HaxeFlixel/flixel@7c7130e529055642f1b8efbeece0efc186aac72b
FlxButtonPlus: fix initial text visibility, add setters for the member objects to allow replacing the instances (thanks @l0rb)