Fixed gamepad to use this.length instead of members.length when calculating alpha.
Fixed set_alpha for FlxGamePad to account for null members.
Merge pull request #657 from newtzgames/master

Fixed FlxGamePad alpha calculation.
Merge remote-tracking branch 'origin/master' into dev

Conflicts:
	src/org/flixel/system/input/FlxGamePad.hx